OFFSET
1,2
LINKS
Fung Lam, Table of n, a(n) for n = 1..1000
FORMULA
D-finite with recurrence 54*n*(n-1)*a(n) -3*(n-1)*(160*n-237)*a(n-1) +3*(-422*n^2+1721*n-1713)*a(n-2) +2*(-67*n^2+388*n-552)*a(n-3) +(137*n^2-1352*n+3279)*a(n-4) +(7*n-37)*(n-6)*a(n-5) -(n-6)*(n-7)*a(n-6)=0. - R. J. Mathar, Mar 24 2023
MATHEMATICA
Rest[CoefficientList[InverseSeries[Series[x*(1-2*x-5*x^2)/(1-x^2), {x, 0, 20}], x], x]] (* Vaclav Kotesovec, Jan 29 2014 *)
PROG
(Python)
# R. J. Mathar, 2023-03-28
class A235348() :
def __init__(self) :
self.a = [1, 2, 12, 82, 636, 5266]
def at(self, n):
if n <= len(self.a):
return self.a[n-1]
else:
rhs = -3*(n-1)*(160*n-237)*self.at(n-1) \
+3*(-422*n**2+1721*n-1713)*self.at(n-2) \
+2*(-67*n**2+388*n-552)*self.at(n-3) \
+(137*n**2-1352*n+3279)*self.at(n-4) \
+(7*n-37)*(n-6)*self.at(n-5) -(n-6)*(n-7)*self.at(n-6)
rhs //= (-54*n*(n-1))
self.a.append(rhs)
return self.a[-1]
a235348 = A235348()
for n in range(1, 12):
print(a235348.at(n))
# a235348.
(PARI) Vec( serreverse(x*(1-2*x-5*x^2)/(1-x^2) +O(x^66) ) ) \\ Joerg Arndt, Jan 14 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Fung Lam, Jan 13 2014
STATUS
approved