OFFSET
0,2
COMMENTS
Convolution of triangular numbers (A000217) and 11-gonal numbers (A051682). - Bruno Berselli, Jul 21 2015
REFERENCES
A. H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, pp. 194-196.
Herbert John Ryser, Combinatorial Mathematics, "The Carus Mathematical Monographs", No. 14, John Wiley and Sons, 1963, pp. 1-16.
LINKS
Kelvin Voskuijl, Table of n, a(n) for n = 0..10000
Index entries for linear recurrences with constant coefficients, signature (6,-15,20,-15,6,-1).
FORMULA
a(n) = C(n+4, 4)*(9*n+5)/5.
G.f.: (1+8*x)/(1-x)^6.
E.g.f.: exp(x)*(120 + 1560*x + 2520*x^2 + 1160*x^3 + 185*x^4 + 9*x^5)/120. - Stefano Spezia, Feb 23 2026
MATHEMATICA
Table[((1 + n)(2 + n)(3 + n)(4 + n)(5 + 9 n))/120, {n, 0, 40}] (* Harvey P. Dale, Aug 19 2012, corrected by Kelvin Voskuijl, Feb 18 2026 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Barry E. Williams, Dec 14 1999
EXTENSIONS
More terms from Kelvin Voskuijl, Feb 18 2026
STATUS
approved