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 A275342 #6 Jul 23 2016 20:50:03 %S A275342 1,0,1,0,0,2,1,0,0,0,0,2,1,0,1,0,0,0,3,2,1,0,0,2,1,0,1,0,0,0,2,1,0,0, %T A275342 0,1,0,0,1,0,2,1,0,0,2,1,0,2,1,0,0,2,1,0,0,0,3,2,1,0,1,0,1,0,0,0,0,1, %U A275342 0,0,1,0,0,0,0,2,1,0,0,0,1,0,0,2,1,0,1,0,3,2,1,0,0,0,1,0,0,0,2,1,0,2,1,0,0,0,0,2,1,0,0,4,3,2,1,0,0,4,3,2,1,0,2,1,0,1,0,0,0,1 %N A275342 2-adic valuation of iterated triangular numbers, starting with 2. %F A275342 Writing t(1) = 2, t(n+1) = t(n)(t(n)+1)/2, the sequence is nu_2 (t(n)), where nu_2 (x) is the exponent of the highest power of 2 dividing x. %F A275342 a(n) = A007814(A007501(n)). - _Michel Marcus_, Jul 23 2016 %e A275342 t(1) = 2, t(2) = 3, t(3) = 6, t(4) = 21, so a(1) = 1, a(2) = 0, a(3) = 1, a(4) = 0. %Y A275342 Cf. A007501, A007814, A117872. %K A275342 nonn %O A275342 1,6 %A A275342 _Jeffrey Shallit_, Jul 23 2016