OFFSET
0,2
COMMENTS
Diagonal sums of A114193.
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: 4/(2+x-(x-2)*sqrt(1+8*x)).
Conjecture: 6*(n+1)*a(n) + (37n-29)*a(n-1) + 2*(45-41n)*a(n-2) + (47n-87)*a(n-3) + 4*(5-2n)*a(n-4) = 0. - R. J. Mathar, Dec 10 2011
a(n) ~ 17 * (-1)^n * 2^(3*n+4) / (225 * sqrt(Pi) * n^(3/2)). - Vaclav Kotesovec, Feb 03 2014
MATHEMATICA
CoefficientList[Series[4/(2+x-(x-2)*Sqrt[1+8*x]), {x, 0, 20}], x] (* Vaclav Kotesovec, Feb 03 2014 *)
PROG
(PARI) x='x+O('x^50); Vec(4/(2+x-(x-2)*sqrt(1+8*x))) \\ G. C. Greubel, Mar 17 2017
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Nov 16 2005
STATUS
approved