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 A257591 #17 Jun 19 2015 04:58:17
%S A257591 15,35,39,45,51,55,63,65,75,85,87,91,95,99,105,111,115,117,119,123,
%T A257591 135,143,145,147,153,155,159,165,171,175,183,185,187,189,195,203,205,
%U A257591 207,215,219,221,225,231,235,245,247,255,259,261,265,267,273,275,279,285
%N A257591 Odd numbers which are not prime powers but which have a proper divisor == 1 mod 4.
%H A257591 Hiroaki Yamanouchi, <a href="/A257591/b257591.txt">Table of n, a(n) for n = 1..3124</a>
%H A257591 R. Lauterbach, <a href="http://dx.doi.org/10.1007/s10884-014-9402-1">Equivariant Bifurcation and Absolute Irreducibility in R^8: A Contribution to Ize Conjecture and Related Bifurcations</a>, Journal of Dynamics and Differential Equations, Oct 2014; DOI 10.1007/s10884-014-9402-1.
%e A257591 63 = 7*9 is not a power of a prime and has a proper divisor 9 == 1 mod 4.
%o A257591 (PARI) lista(nn) = {forstep(n=1, nn, 2, if (!isprimepower(n) && sumdiv(n, d, (d != 1) && (d != n) && ((d % 4)==1)), print1(n, ", ")););} \\ _Michel Marcus_, Jun 19 2015
%Y A257591 Subsequence of A061346.
%K A257591 nonn
%O A257591 1,1
%A A257591 _N. J. A. Sloane_, May 14 2015
%E A257591 a(7)=57 removed and a(11)-a(55) added by _Hiroaki Yamanouchi_, May 20 2015