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A226301
a(n) = A182107(4n+1).
2
2, 20, 210, 2460, 31122, 410378, 5575682, 77445152, 1093987598, 15660579168, 226608224226, 3308255447206, 48658330768786, 720224064591558, 10718841444208526, 160283814975116386, 2406806389622598056, 36273856567768931782, 548495166665709003794, 8318227159058988730096
OFFSET
1,1
LINKS
MATHEMATICA
S[0, 0] = 1; S[0, _] = 0; S[n_, k_] /; k < 0 || k > Binomial[n + 1, 2] = 0; S[n_, k_] := S[n, k] = S[n - 1, k] + S[n - 1, k - n];
b[n_] := 2 Sum[Sum[k2 = (n^2 - n)/4 - (n - i - 1) - k1; S[n - i - 2, k1] * S[i - 1, k2], {k1, 0, (n^2 - n)/4 - (n - i - 1)}] + Sum[k2 = (n^2 - n)/4; S[Floor[(n - 2)/2], k1] * S[Floor[(n - 2)/2], k2], {k1, 0, (n^2 - n)/4}], {i, 1, Floor[(n - 1)/2]}];
a[n_] := b[4n+1];
Table[a[n], {n, 1, 20}] (* Jean-François Alcover, Feb 23 2019 *)
CROSSREFS
Sequence in context: A077327 A173499 A067636 * A000906 A308945 A356853
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 06 2013
STATUS
approved