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A046996 Number of Baxter permutations: A001181/2. 2
1, 3, 11, 46, 211, 1037, 5377, 29101, 163120, 941480, 5570280, 33664996, 207249719, 1296670793, 8229378293, 52895993341, 343891293422, 2258771535962, 14974619271658, 100117092310368, 674548712552456 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

Table of n, a(n) for n=2..22.

MATHEMATICA

Sum[Binomial[n+1, k-1] Binomial[n+1, k] Binomial[n+1, k+1], {k, 1, n}]/(2 Binomial[n+1, 1] Binomial[n+1, 2])

CROSSREFS

Sequence in context: A281548 A086521 A225293 * A248426 A337913 A129579

Adjacent sequences:  A046993 A046994 A046995 * A046997 A046998 A046999

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Olivier Gérard, Jun 26 2001

STATUS

approved

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Last modified May 17 22:15 EDT 2021. Contains 343992 sequences. (Running on oeis4.)