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 A141517 #6 Oct 04 2015 00:06:50 %S A141517 1,1,1,1,1,1,1,1,1,1,23,1,1,1,1,1,1,1,1,5,1,1,47,1,1,1,1,1,1,1,1,1,23, %T A141517 1,71,73,1,1,1,5,1,7,431,1,1,1,1,97,1,1,1,1,1,1,23,1,1,1,1,5,1,1,1,1, %U A141517 1,1,1,1,47,1,1,1,1,1,601,1,23,1,1,5,1,1,167,7,1,431,1,1,1,1,1,1,1,1,191,193,1 %N A141517 A141498(n)/A027760(n). %C A141517 Composite entries are a(100)=25, a(120)=1205, a(144)=55969, a(156)=4069 etc. %p A141517 A010696 := proc(n) op( (n mod 2)+1,[2,6]) ; end: A086892 := proc(n) gcd(2^n-1,3^n-1) ; end: %p A141517 A141498 := proc(n) A010696(n-1)* A086892(n) ; end: A027760 := proc(n) local s, p; s := 0 ; p := 2; while p <= n+1 do if n mod (p-1) = 0 then s := s+1/p; fi; p := nextprime(p) ; od: denom(s) ; end: %p A141517 A141517 := proc(n) A141498(n)/A027760(n) ; end: seq(A141517(n),n=1..120) ; # _R. J. Mathar_, Sep 03 2009 %K A141517 nonn %O A141517 1,11 %A A141517 _Paul Curtz_, Aug 11 2008 %E A141517 Offset modified, extended by _R. J. Mathar_, Sep 03 2009