A376541 Natural numbers whose iterated squaring modulo 1000 eventually enters the 4-cycle 201, 401, 801, 601.

7, 43, 49, 51, 93, 99, 101, 107, 143, 149, 151, 157, 199, 201, 207, 243, 257, 293, 299, 301, 343, 349, 351, 357, 393, 399, 401, 407, 449, 451, 457, 493, 507, 543, 549, 551, 593, 599, 601, 607, 643, 649, 651, 657, 699, 701, 707, 743, 757, 793, 799, 801, 843

Offset

1,1

Comments

The natural numbers decompose into eight categories under the operation of repeated squaring modulo 1000, four of which consist of numbers that eventually settle at the attractors 0 (cf. A008592), 1 (cf. A376538), 376 (cf. A376539), or 625 (cf. A017329), two of which eventually enter one of the 4-cycles 176, 976, 576, 776 (cf. A376540) or 201, 401, 801, 601 (this sequence), and two of which eventually enter one of the 20-cycles 16, 256, 536, 296, 616, 456, 936, 96, 216, 656, 336, 896, 816, 856, 736, 696, 416, 56, 136, 496 (cf. A376508) or 41, 681, 761, 121, 641, 881, 161, 921, 241, 81, 561, 721, 841, 281, 961, 521, 441, 481, 361, 321 (cf. A376509).

The first-order differences of the numbers in this sequence repeat with a fixed period of length sixteen: 36, 6, 2, 42, 6, 2, 6, 36, 6, 2, 6, 42, 2, 6, 36, 14, ...

Links

Table of n, a(n) for n=1..53.

Index entries for linear recurrences with constant coefficients, signature (1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -1).

Example

7^2 = 49 -> 49^2 = 401 -> 401^2 = 801 -> 801^2 = 601 -> 601^2 = 201 -> 201^2 = 401 -> ... (mod 1000).

Crossrefs

Cf. A008592, A017329, A376506, A376507, A376508, A376509, A376538, A376539, A376540.

Sequence in context: A175159 A173828 A376506 * A045800 A159254 A062336

Adjacent sequences: A376538 A376539 A376540 * A376542 A376543 A376544

Keyword

nonn

Author

Martin Renner, Sep 26 2024

Status

approved