A391345 Numbers k that are multiples of 5 and for which Stern polynomial B(k,x) is irreducible.

5, 25, 55, 65, 95, 115, 125, 145, 175, 185, 205, 215, 235, 245, 265, 295, 305, 335, 395, 415, 425, 445, 475, 485, 505, 515, 545, 575, 625, 655, 665, 695, 755, 785, 805, 815, 865, 875, 895, 905, 925, 935, 955, 965, 985, 995, 1025, 1045, 1055, 1075, 1085, 1135, 1145, 1165, 1225, 1255, 1295, 1345, 1375, 1405, 1415

Offset

1,1

Links

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

Formula

a(n) = 5*A391341(n).

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_A391345(n) = (!(n%5) && polisirreducible(ps(n)));

Crossrefs

Cf. A391341.

Intersection of A008587 and A186891.

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

Sequence in context: A225494 A139479 A078569 * A044082 A161143 A045576

Adjacent sequences: A391342 A391343 A391344 * A391346 A391347 A391348

Keyword

nonn

Author

Antti Karttunen, Dec 12 2025

Status

approved