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 A128568 Column 1 of triangle A128567. 3
 1, 6, 31, 133, 587, 2531, 10950, 47185, 203704, 879711, 3804530, 16464710, 71312805, 309083291, 1340546867, 5817555402, 25258769216, 109711224970, 476675868834, 2071569641859, 9004430215111, 39144480326143, 170184867215647, 739924236443359, 3217001700174226 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS A128567 is the matrix square of Parker's partition triangle A047812. LINKS FORMULA a(n) = Sum_{s=1..n+1} A047812(n+2,s)*A047812(s+1,1) = Sum_{s=1..n+1} A047812(n+2,s)*A007042(s+1) for n >= 0. - Petros Hadjicostas, May 31 2020 PROG (PARI) {a(n)=local(M); M=matrix(n+2, n+2, r, c, if(r

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Last modified January 22 07:09 EST 2021. Contains 340360 sequences. (Running on oeis4.)