OFFSET
1,2
COMMENTS
Geometrically, the partial sums of A006564 may be interpreted as 4-dimensional icosahedral hyperpyramidal numbers.
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1).
FORMULA
a(n) = Sum_{k=1..n} A006564(k).
From Colin Barker, Aug 15 2018: (Start)
G.f.: x*(1 + 8*x + 6*x^2) / (1 - x)^5.
a(n) = n*(2 - 3*n + 10*n^2 + 15*n^3)/24.
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>5.
(End)
PROG
(PARI) Vec(x*(1 + 8*x + 6*x^2) / (1 - x)^5 + O(x^40)) \\ Colin Barker, Aug 15 2018
(PARI) a(n) = (n*(2 - 3*n + 10*n^2 + 15*n^3)) / 24 \\ Colin Barker, Aug 15 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Alejandro J. Becerra Jr., Aug 15 2018
STATUS
approved