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A188478
Binomial variation of the Catalan numbers
2
1, 1, 1, 2, 4, 11, 33, 116, 456, 1999, 9623, 50603, 288287, 1769352, 11636669, 81652911, 608857325, 4807873069, 40080193414, 351751992542, 3241754135966, 31301851579056, 316012152140592, 3329322705562603, 36539984716325869, 417102552119591395, 4944630222121834001, 60791493200390178470
OFFSET
0,4
LINKS
FORMULA
a(n) = sum( binomial(n-1-i, i)*a(i)*a(n-1-i), i=0..(n-1) ) with a(0)=1
MATHEMATICA
a[0] = 1; a[n_] := a[n] = Sum[ Binomial[n - i - 1, i] a[i]*a[n - 1 - i], {i, 0, n - 1}]; Table[a[i], {i, 0, 30}]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Olivier Gérard, Apr 01 2011
STATUS
approved