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 A037281 #10 Aug 09 2017 00:17:47
%S A037281 0,0,0,1,0,1,0,1,1,2,0
%N A037281 Number of iterations of transformation in A037280 needed to reach 1 or a prime, or -1 if no such number exists.
%C A037281 Continuation from a(12): -1, 0, 3, 4, 1, 0, -1, 0, -1, 1, 1, 0, -1, 1, 4, 2, -1, 0, -1, 0, 2, 1, -1, 3, -1, 0, 2, 1, -1, 0, -1, 0, -1, -1, 1, 0, -1, 1, -1, 1, -1, 0, 1, 2, -1, 2, 1, 0, -1; where all the -1's are conjectural. - _Franklin T. Adams-Watters_, Jul 28 2011
%p A037281 with(numtheory):ds:=proc(s) local j: RETURN(add(s[j]*10^(j-1),j=1..nops(s))):end: a:=proc(n) options remember: local d,i,l,m: if n<3 then RETURN(1) else if not isprime(n) then d:=divisors(n): l:=nops(d): m:=ds([seq(op(convert(d[l-i+1],base,10)),i=2..l-1)]): RETURN(m/piecewise(m mod 2=1,1,2^(ifactors(m)[2][1][2]))) else RETURN(n) fi fi: end; for n from 1 to 11 do m:=n: for i from 0 while(not isprime(m) and m<>1) do m:=a(m) od: printf("%d, ",i) od: # C. Ronaldo
%Y A037281 Cf. A037279.
%K A037281 nonn,base,more
%O A037281 1,10
%A A037281 _N. J. A. Sloane_
%E A037281 Corrected by C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 29 2004