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 A078681 #6 Mar 30 2012 18:39:11 %S A078681 1,1,1,53,5,52,1,4,51,2,1,3,39,50,1,162,3,2,1,38,49,4,2,161,50,2,1,52, %T A078681 4,37,1,48,3,13,1,160,9,49,1,8,42,51,18,3,36,8,1,47,3,2,12,35,27,159, %U A078681 1,8,48,2,1,7,4,41,50,16,17,2,1,35,7,13,1,46,11,2,1,3,11,34,2,26,158,7,6,7 %N A078681 Start with n; iterate the process x -> ceiling(3x/2) until reach a prime. Sequence gives number of steps to reach a prime or 0 if no prime is ever reached. %o A078681 (PARI) a(n)=if(n<0,0,s=n; c=1; while(isprime(ceil(3*s/2))==0,s=ceil(3*s/2); c++); c) %Y A078681 Cf. A050412. %K A078681 nonn %O A078681 1,4 %A A078681 _Benoit Cloitre_, Dec 17 2002