A391337 Odd semiprimes p*q, such that Stern polynomial B(p*q,x) is irreducible.

25, 55, 65, 77, 91, 95, 115, 121, 133, 143, 145, 161, 169, 185, 203, 205, 209, 215, 235, 247, 253, 265, 289, 295, 299, 301, 305, 319, 323, 329, 335, 361, 377, 391, 395, 407, 415, 427, 445, 451, 469, 473, 485, 493, 505, 515, 517, 529, 533, 545, 551, 559, 581, 583, 623, 629, 649, 655, 667, 671, 679, 689, 695, 697, 703

Offset

1,1

Comments

There are no multiples of 3 in this sequence because there are no nontrivial multiples of 3 in A186891. See also A391339.

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Prog

(PARI)
memo_for_ps = Map();
ps(n) = if(n<2, n, my(v); if(mapisdefined(memo_for_ps, n, &v), v, v = if(n%2, ps(n\2)+ps(n\2+1), 'x*ps(n\2)); if(n%2, mapput(memo_for_ps, n, v)); (v))); \\ Only memoize on odd n...
is_A391337(n) = ((n%2) && 2==bigomega(n) && polisirreducible(ps(n)));

Crossrefs

Setwise difference A046315 \ A391336.

Intersection of A186891 and A046315.

Subsequence of A391330.

Subsequence of A186892, and of A391258 from which this differs first at n=43, where a(43) = 485, while A391258(43) = 481, value missing from this sequence.

Cf. A391338, A391339.

Cf. A125184, A260443 for a description of Stern polynomials.

Sequence in context: A371129 A186892 A391258 * A206075 A391254 A276448

Adjacent sequences: A391334 A391335 A391336 * A391338 A391339 A391340

Keyword

nonn

Author

Antti Karttunen, Dec 08 2025

Status

approved