A391333 Odd semiprimes k = p*q, with p, q primes, such that either k = A325820(p,x) or k = A325820(q,x) for some x, where A325820 is the carryless base-3 multiplication.

9, 15, 21, 33, 39, 51, 55, 57, 69, 85, 87, 91, 93, 111, 119, 123, 129, 141, 159, 161, 177, 183, 201, 213, 215, 219, 237, 247, 249, 267, 291, 301, 303, 309, 321, 327, 339, 371, 377, 381, 393, 395, 403, 411, 417, 447, 453, 471, 481, 489, 501, 519, 537, 543, 553, 565, 573, 579, 591, 597, 611, 633, 635, 669, 671, 681

Offset

1,1

Links

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

Index entries for sequences related to carryless arithmetic.

Prog

(PARI) is_A391333(n) = if(!(n%2) || 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

Setwise difference A046315 \ A391334.

Cf. A325820.

Subsequences: A391332, A391335 (terms that are not multiples of 3).

Cf. also A391253 (analogous sequence for the carryless base-2 multiplication).

Sequence in context: A391336 A391257 A096788 * A050991 A033553 A391332

Adjacent sequences: A391330 A391331 A391332 * A391334 A391335 A391336

Keyword

nonn,base

Author

Antti Karttunen, Dec 07 2025

Status

approved