PUZZLE #3435: FHSS Frequency Hopping (diff 4)

fhss learn difficulty: 4/7 simulate author: system unsolved

6 characters transmitted over 26 channels (8 jammed). Each character sent 3 times. LCG seed 1642 governs the hop schedule.

DATA

Hop Frequencies	`21, 16, 9, 16, 25, 12, 15, 6, 17, 6, 3, 18, 13, 6, 1, 4, 15, 8`
Transmissions	{'hop': 0, 'freq': 21, 'char_idx': 0, 'char': 'K', 'jammed': False}, {'hop': 1, 'freq': 16, 'char_idx': 1, 'char': 'Q', 'jammed': False}, {'hop': 2, 'freq': 9, 'char_idx': 2, 'char': 'X', 'jammed': False}, {'hop': 3, 'freq': 16, 'char_idx': 3, 'char': 'V', 'jammed': False}, {'hop': 4, 'freq': 25, 'char_idx': 4, 'char': 'S', 'jammed': False}, {'hop': 5, 'freq': 12, 'char_idx': 5, 'char': None, 'jammed': True}, {'hop': 6, 'freq': 15, 'char_idx': 0, 'char': 'K', 'jammed': False}, {'hop': 7, 'freq': 6, 'char_idx': 1, 'char': None, 'jammed': True}, {'hop': 8, 'freq': 17, 'char_idx': 2, 'char': None, 'jammed': True}, {'hop': 9, 'freq': 6, 'char_idx': 3, 'char': None, 'jammed': True}, {'hop': 10, 'freq': 3, 'char_idx': 4, 'char': 'S', 'jammed': False}, {'hop': 11, 'freq': 18, 'char_idx': 5, 'char': 'H', 'jammed': False}, {'hop': 12, 'freq': 13, 'char_idx': 0, 'char': 'K', 'jammed': False}, {'hop': 13, 'freq': 6, 'char_idx': 1, 'char': None, 'jammed': True}, {'hop': 14, 'freq': 1, 'char_idx': 2, 'char': 'X', 'jammed': False}, {'hop': 15, 'freq': 4, 'char_idx': 3, 'char': None, 'jammed': True}, {'hop': 16, 'freq': 15, 'char_idx': 4, 'char': 'S', 'jammed': False}, {'hop': 17, 'freq': 8, 'char_idx': 5, 'char': 'H', 'jammed': False}
Jammed Channels	`0, 4, 5, 6, 12, 17, 23, 24`
N Channels	`26`
N Chars	`6`
Redundancy	`3`
Seed	`1642`
Lcg A	`1103515245`
Lcg C	`12345`
Lcg M	`2147483648`
Hint	`LCG: x_i+1 = (a·x_i + c) mod m. Compute hop sequence from seed, find which hops survived jamming. Group surviving letters by char_idx to reconstruct the word.`
Answer Format	`lowercase word, no spaces or punctuation`

{
  "type": "fhss",
  "hop_frequencies": [
    21,
    16,
    9,
    16,
    25,
    12,
    15,
    6,
    17,
    6,
    3,
    18,
    13,
    6,
    1,
    4,
    15,
    8
  ],
  "transmissions": [
    {
      "hop": 0,
      "freq": 21,
      "char_idx": 0,
      "char": "K",
      "jammed": false
    },
    {
      "hop": 1,
      "freq": 16,
      "char_idx": 1,
      "char": "Q",
      "jammed": false
    },
    {
      "hop": 2,
      "freq": 9,
      "char_idx": 2,
      "char": "X",
      "jammed": false
    },
    {
      "hop": 3,
      "freq": 16,
      "char_idx": 3,
      "char": "V",
      "jammed": false
    },
    {
      "hop": 4,
      "freq": 25,
      "char_idx": 4,
      "char": "S",
      "jammed": false
    },
    {
      "hop": 5,
      "freq": 12,
      "char_idx": 5,
      "char": null,
      "jammed": true
    },
    {
      "hop": 6,
      "freq": 15,
      "char_idx": 0,
      "char": "K",
      "jammed": false
    },
    {
      "hop": 7,
      "freq": 6,
      "char_idx": 1,
      "char": null,
      "jammed": true
    },
    {
      "hop": 8,
      "freq": 17,
      "char_idx": 2,
      "char": null,
      "jammed": true
    },
    {
      "hop": 9,
      "freq": 6,
      "char_idx": 3,
      "char": null,
      "jammed": true
    },
    {
      "hop": 10,
      "freq": 3,
      "char_idx": 4,
      "char": "S",
      "jammed": false
    },
    {
      "hop": 11,
      "freq": 18,
      "char_idx": 5,
      "char": "H",
      "jammed": false
    },
    {
      "hop": 12,
      "freq": 13,
      "char_idx": 0,
      "char": "K",
      "jammed": false
    },
    {
      "hop": 13,
      "freq": 6,
      "char_idx": 1,
      "char": null,
      "jammed": true
    },
    {
      "hop": 14,
      "freq": 1,
      "char_idx": 2,
      "char": "X",
      "jammed": false
    },
    {
      "hop": 15,
      "freq": 4,
      "char_idx": 3,
      "char": null,
      "jammed": true
    },
    {
      "hop": 16,
      "freq": 15,
      "char_idx": 4,
      "char": "S",
      "jammed": false
    },
    {
      "hop": 17,
      "freq": 8,
      "char_idx": 5,
      "char": "H",
      "jammed": false
    }
  ],
  "jammed_channels": [
    0,
    4,
    5,
    6,
    12,
    17,
    23,
    24
  ],
  "n_channels": 26,
  "n_chars": 6,
  "redundancy": 3,
  "seed": 1642,
  "lcg_a": 1103515245,
  "lcg_c": 12345,
  "lcg_m": 2147483648,
  "hint": "LCG: x_i+1 = (a\u00b7x_i + c) mod m. Compute hop sequence from seed, find which hops survived jamming. Group surviving letters by char_idx to reconstruct the word.",
  "answer_format": "lowercase word, no spaces or punctuation"
}

author's note: Pool fill: fhss diff 4