A391339 Numbers k such that Stern polynomial B(3*k,x) is not equal to B(3,x) * B(k,x).

5, 7, 10, 11, 14, 15, 17, 19, 20, 21, 22, 25, 27, 28, 29, 30, 31, 33, 34, 37, 38, 39, 40, 41, 42, 43, 44, 45, 47, 49, 50, 53, 54, 55, 56, 57, 58, 60, 61, 62, 63, 65, 66, 67, 68, 69, 71, 74, 75, 76, 77, 78, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 94, 95, 97, 98, 99, 100, 101, 103, 106, 107, 108, 109, 110, 111

Offset

1,1

Comments

Positions of 0's on the third row of array A391260.

If n is present, then 2*n is also present, and vice versa.

See also comments in A391337.

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_A391339(n) = (ps(3*n)!=ps(3)*ps(n));

Crossrefs

Cf. A391260, A391337, A391338 (complement).

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

Cf. also A391349.

Sequence in context: A064479 A056818 A028736 * A028759 A278579 A088707

Adjacent sequences: A391336 A391337 A391338 * A391340 A391341 A391342

Keyword

nonn

Author

Antti Karttunen, Dec 08 2025

Status

approved