OFFSET
0,2
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (1,4,-4,-6,6,4,-4,-1,1).
FORMULA
From Colin Barker, Dec 17 2015: (Start)
a(n) = (1/2)*(200*n^4 - 120*n^3 + 18*n^2) for n even.
a(n) = (1/2)*(200*n^4 + 280*n^3 + 138*n^2 + 28*n + 2) for n odd.
G.f.: 4*x*(81 + 208*x + 2523*x^2 + 1508*x^3 + 4071*x^4 + 680*x^5 + 525*x^6 + 4*x^7) / ((1-x)^5*(1+x)^4).
(End)
MATHEMATICA
Select[Table[(n(5n-3))/2, {n, 0, 60}], EvenQ]^2 (* Harvey P. Dale, Jul 24 2015 *)
PROG
(PARI) concat(0, Vec(4*x*(81+208*x+2523*x^2+1508*x^3+4071*x^4+680*x^5+525*x^6+4*x^7) / ((1-x)^5*(1+x)^4) + O(x^40))) \\ Colin Barker, Dec 17 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
More terms from Patrick De Geest, Aug 17 2000
STATUS
approved