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 A253790 #10 Jan 15 2015 11:41:18 %S A253790 1,3,5,15,27,39,51,63,75,85,87,99,111,123,125,135,147,159,171,183,195, %T A253790 205,207,209,217,219,231,243,245,255,267,279,291,303,315,325,327,329, %U A253790 339,351,363,365,375,387,399,411,423,435,445,447,459,471,481,483,485,495,507,519,531,543,553,555 %N A253790 a(1) = 1; thereafter, odd numbers such that A055396(n) = A001511(n-1). %C A253790 After 1, all such odd numbers whose smallest prime factor A020639(n) = A000040(k+1), where k = A007814(n-1), the 2-adic valuation of the preceding even number. %C A253790 Any odd number present in A253789 must be one of these terms. %H A253790 Antti Karttunen, <a href="/A253790/b253790.txt">Table of n, a(n) for n = 1..10000</a> %o A253790 (Scheme, with _Antti Karttunen_'s IntSeq-library) %o A253790 (define A253790 (MATCHING-POS 1 1 (lambda (n) (or (= 1 n) (and (odd? n) (= (A055396 n) (A001511 (- n 1)))))))) %Y A253790 Cf. A000040, A001511, A007814, A020639, A029747, A055396, A253789. %K A253790 nonn %O A253790 1,2 %A A253790 _Antti Karttunen_, Jan 13 2015