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 A079352 #5 Mar 30 2012 18:39:12 %S A079352 1,2,4,12,24,48,96,192,384,768,1536,4608,9216,18432,36864,73728, %T A079352 147456,294912,589824,1179648,2359296,4718592,9437184,28311552, %U A079352 56623104,113246208,226492416,452984832,905969664,1811939328,3623878656 %N A079352 a(1)=1, then a(n)=3*a(n-1) if n is already in the sequence, a(n)=2*a(n-1) otherwise. %C A079352 Inspired by A079000. Cf. A064437. %F A079352 a(n+1)=3*a(n) for n=3 n of the form 3*2^k - 1, k>=2 . a(n+1)=2*a(n) otherwise. Hence a(n)=3*(3/2)^floor((log(n/3))/log(2))*2^n. %o A079352 (PARI) a(n)=3*(3/2)^floor((log(n)-log(3))/log(2))*2^n %K A079352 nonn %O A079352 1,2 %A A079352 _Benoit Cloitre_, Feb 14 2003