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 A361643 #9 Mar 19 2023 17:47:25 %S A361643 0,1,2,4,1,3,5,8,2,1,6,9,16,3,5,10,17,4,3,9,7,18,12,1,3,5,11,17,6,8, %T A361643 33,2,5,9,3,20,10,1,7,13,19,32,36,65,34,6,129,24,3,5,11,17,68,66,257, %U A361643 7,40,18,33,132,3,9,5,130,14,513,21,258,9,260,3,72,7 %N A361643 The binary expansion of a(n) specifies which primes divide A359804(n). %H A361643 Rémy Sigrist, <a href="/A361643/b361643.txt">Table of n, a(n) for n = 1..10000</a> %H A361643 Rémy Sigrist, <a href="/A361643/a361643.gp.txt">PARI program</a> %F A361643 a(n) = A087207(A359804(n)). %e A361643 The first terms, in decimal and in binary, alongside A359804(n) and its divisibility by small prime numbers, are: %e A361643 n a(n) bin(a(n)) A359804(n) Divisibility by: %e A361643 7 5 3 2 %e A361643 -- ---- --------- ---------- - - - - %e A361643 1 0 0 1 %e A361643 2 1 1 2 X %e A361643 3 2 10 3 X %e A361643 4 4 100 5 X %e A361643 5 1 1 4 X %e A361643 6 3 11 6 X X %e A361643 7 5 101 10 X X %e A361643 8 8 1000 7 X %e A361643 9 2 10 9 X %e A361643 10 1 1 8 X %o A361643 (PARI) See Links section. %Y A361643 Cf. A087207, A359804. %K A361643 nonn,base %O A361643 1,3 %A A361643 _Rémy Sigrist_, Mar 19 2023