A391860 Numbers k such that 49*k = A048720(m, k) for some m, where A048720 is carryless base-2 multiplication.

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 24, 28, 30, 32, 36, 40, 42, 48, 56, 60, 63, 64, 65, 72, 73, 80, 84, 85, 96, 99, 112, 120, 126, 127, 128, 129, 130, 144, 146, 160, 168, 170, 189, 191, 192, 198, 224, 240, 252, 253, 254, 255, 256, 257, 258, 260, 261, 288, 292, 320, 321, 336, 340, 341, 378

Offset

1,3

Comments

If n is a term, then 2*n is also a term, and vice versa. See A391861 for the odd terms.

Links

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

Index entries for sequences defined by congruent products between domains N and GF(2)[X].

Index entries for sequences related to binary expansion of n.

Index entries for sequences related to carryless arithmetic.

Formula

{0 followed by k such that A280500(49*k, k) = m for some m > 0}.

Example

3 is a term as 49*3 = A048720(113,3) = 147.
21 is a term as 49*21 = A048720(81,21) = 1029.
73 is a term as 49*73 = A048720(49,73) = 3577.

Prog

(PARI) is_A391860(k) = (!k || (0==lift(Pol(binary(49*k)*Mod(1, 2)) % Pol(binary(k))*Mod(1, 2))));

Crossrefs

Cf. A048720, A280500.

Subsequences: A114384 (m=81), A391861 (odd terms).

Cf. also A391744, A391858.

Sequence in context: A178861 A178862 A178860 * A178858 A397791 A362710

Adjacent sequences: A391857 A391858 A391859 * A391861 A391862 A391863

Keyword

nonn,base

Author

Antti Karttunen, Dec 21 2025

Status

approved