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A341920 Number of simple strong triangulations of a fixed pentagon with n interior nodes. 2

%I #14 Feb 08 2022 12:13:06

%S 1,5,20,85,385,1836,9120,46805,246675,1328925,7292688,40652780,

%T 229698220,1313175880,7585060680,44212723797,259808593975,

%U 1537840085775,9162371040900,54913015836525,330888232445505,2003659057873200,12187811305300800,74444226847892460,456458831442283860

%N Number of simple strong triangulations of a fixed pentagon with n interior nodes.

%H Andrew Howroyd, <a href="/A341920/b341920.txt">Table of n, a(n) for n = 1..500</a>

%F From _Peter Bala_, Feb 06 2022: (Start)

%F Conjectures:

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

%F 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)

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

%Y Row m = 2 of A210664.

%Y Cf. A000256, A341917.

%K nonn

%O 1,2

%A _Andrew Howroyd_, Feb 24 2021

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Last modified August 9 18:14 EDT 2024. Contains 375044 sequences. (Running on oeis4.)