This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A381935 #15 Mar 12 2025 17:27:07 %S A381935 0,3,6,15,12,30,30,63,24,45,60,55,60,247,126,255,48,85,90,57,120,189, %T A381935 110,253,120,175,494,8127,252,1015,510,1023,96,165,170,105,180,185, %U A381935 114,117,240,205,378,215,220,765,506,14335,240,343,350,765,988,159,16254 %N A381935 For any n > 0, a(n) is the least nontrivial multiple of n whose binary expansion has the same number of nonleading zeros as that of n; a(0) = 0. %C A381935 This sequence is well defined: for any n > 0: write n as m * 2^k for some odd number m; m divides some Mersenne number M > m (see A352217); M * 2^(k + A023416(m)) is a multiple of n with the desired properties, hence a(n) exists. %H A381935 Rémy Sigrist, <a href="/A381935/b381935.txt">Table of n, a(n) for n = 0..8192</a> %H A381935 Rémy Sigrist, <a href="/A381935/a381935.gp.txt">PARI program</a> %F A381935 a(n) = n * A381934(n). %e A381935 The first terms, in decimal and in binary, are: %e A381935 n a(n) bin(n) bin(a(n)) %e A381935 -- ---- ------ --------- %e A381935 0 0 0 0 %e A381935 1 3 1 11 %e A381935 2 6 10 110 %e A381935 3 15 11 1111 %e A381935 4 12 100 1100 %e A381935 5 30 101 11110 %e A381935 6 30 110 11110 %e A381935 7 63 111 111111 %e A381935 8 24 1000 11000 %e A381935 9 45 1001 101101 %e A381935 10 60 1010 111100 %e A381935 11 55 1011 110111 %e A381935 12 60 1100 111100 %e A381935 13 247 1101 11110111 %e A381935 14 126 1110 1111110 %e A381935 15 255 1111 11111111 %e A381935 16 48 10000 110000 %o A381935 (PARI) \\ See Links section. %Y A381935 Cf. A023416, A161399, A352217, A381934. %K A381935 nonn,base %O A381935 0,2 %A A381935 _Rémy Sigrist_, Mar 10 2025