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 A160465 #10 Jun 02 2025 01:40:02 %S A160465 -1,-11,-114,-3963,-104745,-3926745,-198491580,-26045435115, %T A160465 -2153099119815,-219022225836750,-26891482281048000, %U A160465 -3921682257253270125,-670160622793156369875,-132649536458654226136125 %N A160465 First left hand column of the Eta triangle A160464. %p A160465 nmax:=15; c(2) := -1/3: for n from 3 to nmax do c(n) := (2*n-2)*c(n-1)/(2*n-1)-1/ ((n-1)*(2*n-1)) end do: for n from 2 to nmax do GCS(n-1) := ln(1/(2^(-(2*(n-1)-1-floor(ln(n-1)/ ln(2))))))/ln(2); p(n) := 2^(-GCS(n-1))*(2*n-1)!; ETA(n, 1) := p(n)*c(n) end do: seq(ETA(n, 1), n=2..nmax); %Y A160465 A160464 is the Eta triangle. %Y A160465 The GCS(n) sequence equals the geometric Connell sequence A049039(n). %Y A160465 The p(n) sequence is given by A160473. %K A160465 easy,sign %O A160465 2,2 %A A160465 _Johannes W. Meijer_, May 24 2009