VOOZH about

URL: https://oeis.org/A391737

⇱ A391737 - OEIS

login
A391737
Numbers k such that 25*k = A048720(25, k), where A048720 is carryless base-2 multiplication.
7
0, 1, 2, 4, 5, 8, 10, 16, 20, 32, 33, 40, 64, 65, 66, 80, 128, 129, 130, 132, 133, 160, 161, 256, 257, 258, 260, 261, 264, 266, 320, 321, 322, 512, 513, 514, 516, 517, 520, 522, 528, 532, 640, 641, 642, 644, 645, 1024, 1025, 1026, 1028, 1029, 1032, 1034, 1040, 1044, 1056, 1057, 1064, 1280, 1281, 1282, 1284, 1285
OFFSET
1,3
COMMENTS
Numbers k such that k XOR 8*k XOR 16*k = 25*k.
If n is a term, then 2*n is also a term, and vice versa.
PROG
(PARI)
A048720(b, c) = fromdigits(Vec(Pol(binary(b))*Pol(binary(c)))%2, 2);
is_A391737(k) = (25*k == A048720(25, k));
(PARI) is_A391737(n) = (bitxor(n, bitxor(8*n, 16*n))==25*n);
CROSSREFS
Cf. A048720.
Subsequence of A115831. The first terms that occur in A115831 but not here are 143, 285, and 286.
Subsequence of A391858.
Cf. also A115422, and A391738, A391739.
Sequence in context: A018433 A228939 A115831 * A094958 A018565 A018391
KEYWORD
nonn,base
AUTHOR
Antti Karttunen, Dec 21 2025
STATUS
approved