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 A253092 #11 Feb 15 2015 10:30:57
%S A253092 0,0,1,0,1,2,1,2,3,1,2,3,2,3,4,3,4,5,3,4,5,4,5,6,5,6,7,4,5,6,5,6,7,6,
%T A253092 7,8,6,7,8,7,8,9,8,9,10,8,9,10,9,10,11,10,11,12,9,10,11,10,11,12,11,
%U A253092 12,13,11,12,13,12,13,14,13,14,15,13,14,15,14,15,16
%N A253092 Log_3(A133579(n)).
%C A253092 Using the definition of A133579 this amounts to a(n) = a(n-1)-valuation_3(n) if n=3k, and a(n) = a(n-1)+1 else. - _M. F. Hasler_, Feb 15 2015
%H A253092 M. F. Hasler, <a href="/A253092/b253092.txt">Table of n, a(n) for n = 0..3000</a>
%e A253092 a(18)=a(17)-2 because 18=3^2, a(81)=a(80)-4 because 81=3^4.
%t A253092 nxt[{n_, a_}] := {n + 1, If[CoprimeQ[a, n + 1], 3 a, a/GCD[a, n + 1]]}; Log[3,#]&/@Join[{1},Transpose[NestList[nxt,{1,1},80]][[2]]] (* _Harvey P. Dale_, Feb 14 2015 *)
%o A253092 (PARI) a=-1;A253092=vector(1000,n,a+=if(n%3,1,-valuation(n,3))) \\ _M. F. Hasler_, Feb 15 2015
%Y A253092 Cf. A133579.
%K A253092 nonn
%O A253092 0,6
%A A253092 _N. J. A. Sloane_, Feb 14 2015