A391340 Odd numbers k such that Stern polynomial B(3*k,x) is equal to B(3,x) * B(k,x).

1, 3, 9, 13, 23, 35, 51, 59, 73, 79, 93, 105, 141, 183, 205, 279, 291, 371, 407, 419, 563, 585, 733, 745, 819, 841, 1117, 1129, 1165, 1311, 1463, 1485, 1629, 1641, 1677, 2149, 2231, 2253, 2327, 2339, 2353, 2931, 2967, 2979, 3109, 3255, 3277, 3351, 3363, 3781, 4467, 4503, 4515, 4659, 4681, 5041, 5853, 5865, 5939, 5961

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..745

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_A391340(n) = (n%2 && (ps(3*n)==ps(3)*ps(n)));

Crossrefs

Odd terms of A391338.

Cf. A391260.

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

Sequence in context: A135370 A206802 A285900 * A022408 A126827 A363628

Adjacent sequences: A391337 A391338 A391339 * A391341 A391342 A391343

Keyword

nonn

Author

Antti Karttunen, Dec 08 2025

Status

approved