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.
A215406 := proc(n) local m,a,y,t,x,u,v; m := iquo(A070939(n), 2); a := A030101(n); y := 0; t := 1; for x from 0 to 2*m-2 do if irem(a, 2) = 1 then y := y + 1 else u := 2*m - x; v := m-1 - iquo(x+y,2); t := t + A037012(u,v); y := y - 1 fi; a := iquo(a, 2) od; A014137(m) - t end: seq(A215406(i),i=0..199); # Peter Luschny, Aug 10 2012
A215406[n_] := Module[{m, d, a, y, t, x, u, v}, m = Quotient[Length[d = IntegerDigits[n, 2]], 2]; a = FromDigits[Reverse[d], 2]; y = 0; t = 1; For[x = 0, x <= 2*m - 2, x++, If[Mod[a, 2] == 1, y++, u = 2*m - x; v = m - Quotient[x + y, 2] - 1; t = t - Binomial[u - 1, v - 1] + Binomial[u - 1, v]; y--]; a = Quotient[a, 2]]; (1 - I*Sqrt[3])/2 - 4^(m + 1)*Gamma[m + 3/2]*Hypergeometric2F1[1, m + 3/2, m + 3, 4]/(Sqrt[Pi]*Gamma[m + 3]) - t]; Table[A215406[n] // Simplify, {n, 0, 86}] (* Jean-François Alcover, Jul 25 2013, translated and adapted from Peter Luschny's Maple program *)
def A215406(n) : # CatalanRankGlobal(n) m = A070939(n)//2 a = A030101(n) y = 0; t = 1 for x in (1..2*m-1) : u = 2*m - x; v = m - (x+y+1)/2 mn = binomial(u, v) - binomial(u, v-1) t += mn*(1 - a%2) y -= (-1)^a a = a//2 return A014137(m) - t
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