A341920 Number of simple strong triangulations of a fixed pentagon with n interior nodes.
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
Offset: 1
Keywords
Links
- Andrew Howroyd, Table of n, a(n) for n = 1..500
Programs
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PARI
R(25,2) \\ R defined in A210664.
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)