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 A242016 #21 Oct 11 2019 02:18:07 %S A242016 3,3,3,7,3,23,3,3,7,3,3,3,7,3,47,3,31,3,7,3,233,3,3,7,3,31,3,223,3,7, %T A242016 3,13367,3,431,3,7,3,2351,3,127,3,7,3,6361,3,23,3,7,3,179951,3,3,7,3, %U A242016 31,3,193707721,3,7,3 %N A242016 Smallest prime factor of A135972(n), the n-th composite Mersenne number. %H A242016 Chai Wah Wu, <a href="/A242016/b242016.txt">Table of n, a(n) for n = 1..1201</a> %F A242016 a(n) = A020639(A135972(n)). %o A242016 (PARI) for(n=2, 1e2, if(!ispseudoprime(2^n-1), p=factor(2^n-1)[1, 1]; print1(p, ", "))) %Y A242016 Cf. A135972, A242017. Subsequence of A056608. %K A242016 nonn %O A242016 1,1 %A A242016 _Felix Fröhlich_, Aug 11 2014