OFFSET
3,2
LINKS
Chai Wah Wu, Table of n, a(n) for n = 3..1000
Geir Ellingsrud and Stein Arild Stromme, Bott's formula and enumerative geometry, J. Amer. Math. Soc. 9 (1996), 175-193. [arXiv:alg-geom/9411005]
Index entries for linear recurrences with constant coefficients, signature (9,-36,84,-126,126,-84,36,-9,1).
FORMULA
a(n) = (n-3)*(n+6)*(n^6-3*n^5-33*n^4+135*n^3+161*n^2-1257*n+1320)/24 .
a(n) = 9*a(n-1)-36*a(n-2)+ 84*a(n-3)-126*a(n-4)+126*a(n-5)-84*a(n-6)+36*a(n-7)-9*a(n-8)+a(n-9), n>=12 [Harvey P. Dale, Oct 20 2011]
G.f.: x^4*(-10*x^7 +279*x^6 -1071*x^5 +879*x^4 +1724*x^3 -2331*x^2 -1115*x - 35)/(x-1)^9 [Harvey P. Dale, Oct 20 2011]
MATHEMATICA
Table[(n^8-60n^6+90n^5+1160n^4-3204n^3-5349n^2+26586n-23760)/24, {n, 3, 30}] (* or *) LinearRecurrence[{9, -36, 84, -126, 126, -84, 36, -9, 1}, {0, 35, 1430, 13941, 75205, 289800, 897165, 2379300, 5620846}, 30] (* Harvey P. Dale, Oct 20 2011 *)
PROG
(Python)
from itertools import islice
def A135923_generator():
m = [1680, -840, -1380, -240, 641, 393, -209, -10, 0]
yield m[-1]
while True:
for i in range(8):
m[i+1]+= m[i]
yield m[-1]
list(islice(A135923_generator(), 0, 50, 1)) # Chai Wah Wu, Nov 14 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Mar 07 2008
STATUS
approved