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 A236839 #7 Apr 27 2014 09:57:47 %S A236839 43,79,86,89,125,135,149,158,172,178,181,209,227,235,250,263,270,281, %T A236839 293,298,311,316,317,331,344,349,356,362,371,383,393,399,401,418,421, %U A236839 443,447,454,470,479,493,500,509,519,521,523,526,540,547,562,567,577,586,596,609 %N A236839 Numbers that occur as results of downward remultiplication (N -> GF(2)[X]) of some number and have at least one irreducible polynomial factor encoded by a composite number. %C A236839 Terms of A236841 that are found in A236838. %H A236839 Antti Karttunen, <a href="/A236839/b236839.txt">Table of n, a(n) for n = 1..1605</a> %e A236839 43, which is A234741(43), and in binary '101011', encodes polynomial x^5 + x^3 + x + 1, which factors as (x + 1)(x^4 + x^3 + 1), i.e. 43 = A048720(3,25), and the latter factor of these, encoded by 25, is a composite in N, thus 43 is a term of this sequence. %o A236839 (Scheme, with _Antti Karttunen_'s IntSeq-library) %o A236839 (define A236839 (COMPOSE A236841 (MATCHING-POS 1 2 (lambda (n) (any (lambda (p) (= 1 (A066247 p))) (GF2Xfactor (A236841 n))))))) %Y A236839 Setwise difference A236838 \ A236834, and also A236841 \ A236850. %Y A236839 Cf. A236838, A236841, A236849. %K A236839 nonn %O A236839 1,1 %A A236839 _Antti Karttunen_, Feb 02 2014