A325386 Numbers n such that for any divisor d of n and some k, A048720(d,k) = n only for trivial cases d=1 and d=n, despite that n is neither prime nor in A014580.

69, 77, 81, 121, 169, 205, 209, 261, 265, 275, 289, 295, 305, 321, 323, 327, 329, 339, 377, 405, 407, 437, 453, 473, 475, 481, 493, 517, 533, 551, 553, 555, 559, 565, 575, 581, 583, 595, 625, 649, 667, 671, 699, 703, 707, 737, 747, 749, 755, 763, 767, 779, 785, 805, 815, 833, 835, 849, 851, 855, 861, 869, 871, 885, 893, 905, 923, 925

Offset: 1

Author

Antti Karttunen, May 11 2019

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..20000
• Index entries for sequences related to polynomials in ring GF(2)[X]

Crossrefs

Terms of A325559 not in A257688.

Subsequence of A005408 (odd numbers).

Cf. A014580, A325560.

Differs from A260428 for the first time at n=32, where a(32) = 555, a value missing from A260428.

Programs

PARI

A325560(n) = { my(p = Pol(binary(n))*Mod(1, 2)); sumdiv(n,d,my(q = Pol(binary(d))*Mod(1, 2)); !(p%q)); };
isA325386(n) = (!isprime(n) && !polisirreducible(Pol(binary(n))*Mod(1,2)) && (2 == A325560(n)));