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A341920 Number of simple strong triangulations of a fixed pentagon with n interior nodes. 2
1, 5, 20, 85, 385, 1836, 9120, 46805, 246675, 1328925, 7292688, 40652780, 229698220, 1313175880, 7585060680, 44212723797, 259808593975, 1537840085775, 9162371040900, 54913015836525, 330888232445505, 2003659057873200, 12187811305300800, 74444226847892460, 456458831442283860 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..500

FORMULA

From Peter Bala, Feb 06 2022: (Start)

Conjectures:

a(n) = 5*(5*n-3)*binomial(3*n,n)/((n+1)*(2*n+1)*(2*n+3)).

a(n+1) = 3*(3*n+1)*(3*n+2)*(5*n+2)/(2*(n+2)*(2*n+5)*(5*n-3))*a(n). (End)

PROG

(PARI) R(25, 2) \\ R defined in A210664.

CROSSREFS

Row m = 2 of A210664.

Cf. A000256, A341917.

Sequence in context: A126987 A152185 A152187 * A045499 A145932 A026661

Adjacent sequences:  A341917 A341918 A341919 * A341921 A341922 A341923

KEYWORD

nonn

AUTHOR

Andrew Howroyd, Feb 24 2021

STATUS

approved

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Last modified May 27 15:47 EDT 2022. Contains 354106 sequences. (Running on oeis4.)