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A023421 Generalized Catalan Numbers. +0
2
1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 65, 133, 274, 568, 1184, 2481, 5223, 11042, 23434, 49908, 106633, 228505, 490999, 1057683, 2283701, 4941502, 10713941, 23272929, 50642017, 110377543 (list; graph; listen)
OFFSET

0,6

MATHEMATICA

Clear[ a ]; a[ 0 ]=1; a[ n_Integer ] := a[ n ]=a[ n-1 ]+Sum[ a[ k ]*a[ n-2-k ], {k, 3, n-2} ];

CROSSREFS

Cf. A000108, A004148, A004149.

Fourth row of A064645.

Sequence in context: A157021 A006211 A101333 this_sequence A098051 A084637 A100137

Adjacent sequences: A023418 A023419 A023420 this_sequence A023422 A023423 A023424

KEYWORD

nonn,easy

AUTHOR

Olivier Gerard (olivier.gerard(AT)gmail.com)

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Last modified March 20 09:10 EDT 2010. Contains 173642 sequences.


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