A391335 Odd semiprimes k = p*q, with p, q primes > 3, such that either k = A325820(p,x) or k = A325820(q,x) for some x, where A325820 is the carryless base-3 multiplication.

55, 85, 91, 119, 161, 215, 247, 301, 371, 377, 395, 403, 481, 553, 565, 611, 635, 671, 689, 695, 707, 721, 799, 817, 889, 917, 959, 961, 965, 973, 1007, 1043, 1079, 1099, 1115, 1157, 1159, 1169, 1195, 1199, 1267, 1285, 1313, 1337, 1339, 1345, 1355, 1369, 1385, 1391, 1393, 1403, 1415, 1417, 1501, 1535, 1565, 1589

Offset

1,1

Comments

Terms of A391333 that are not multiples of 3.

Links

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

Index entries for sequences related to carryless arithmetic.

Prog

(PARI) is_A391335(n) = if(!(n%2) || !(n%3) || 2!=bigomega(n), 0, my(f=factor(n), a = f[1, 1], b = f[#f~, 1], Pa=Pol(digits(a, 3))*Mod(1, 3), Pb=Pol(digits(b, 3))*Mod(1, 3), Pn=Pol(digits(n, 3))*Mod(1, 3)); ((0==lift(Pn % Pa)) || (0==lift(Pn % Pb))));

Crossrefs

Intersection of A001651 and A391333.

Subsequence of A391330.

Cf. A325820.

Cf. A391331 (subsequence).

Sequence in context: A065912 A245284 A203613 * A366848 A320507 A039533

Adjacent sequences: A391332 A391333 A391334 * A391336 A391337 A391338

Keyword

nonn,base

Author

Antti Karttunen, Dec 07 2025

Status

approved