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 A067321 #9 Dec 11 2019 23:41:05 %S A067321 1,32,3072,429760,71386880,13057591296,2539643772928,515384111218688, %T A067321 107895796673347584,23131454701441122304,5052953723661587578880, %U A067321 1120663604347562971103232,251676943773831910414876672 %N A067321 One-half of odd-indexed members of A067297. %F A067321 a(n) = A067297(2n+1)/2. %F A067321 G.f.: A(x) = (f(y) - f(-y))/y with f(y) := (-1 + 9*y + (1+6*y)*c(y))/((1-y)*(1+5*y)*c(y) - 1 + 11*y - y^2) where c(y) is g.f. of A000108 (Catalan) and y=4*sqrt(x). %Y A067321 Cf. A067320 (even-indexed members of A067297). %K A067321 nonn,easy %O A067321 0,2 %A A067321 _Wolfdieter Lang_, Feb 05 2002