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 A103673 #15 Apr 07 2013 08:16:00 %S A103673 0,0,0,0,0,1,0,0,0,0,1,0,1,0,0,0,0,0,0,0,0,0,1,1,0,1,0,1,0,1,0,0,0,1, %T A103673 1,1,0,1,1,1,1,1,1,1,1,1,0,1,1,1,1,1,1,0,1,1,1,1,0,1,1,1,1,1,1,0,1,1, %U A103673 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1 %N A103673 If in binary representation n! contains 5! then 1 else 0. %C A103673 a(A103676(n)) = 1, a(A103677(n)) = 0. %C A103673 Conjecture: a(n) = 1 for n > 65. - _Charles R Greathouse IV_, Apr 07 2013 %H A103673 <a href="/index/Ch#char_fns">Index entries for characteristic functions</a> %H A103673 <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a> %H A103673 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a> %o A103673 (PARI) a(n)=n=n!;while(n>119, my(e=valuation(n,2),e1=valuation((n>>=e)+1,2)); n>>=e1; if(e>2 && e1>3, return(1))); 0 \\ _Charles R Greathouse IV_, Apr 07 2013 %Y A103673 Cf. A102730, A036603, A007088, A000142, A103674, A103675. %K A103673 nonn,base %O A103673 0,1 %A A103673 _Reinhard Zumkeller_, Feb 12 2005