OFFSET
0,2
COMMENTS
More generally coefficients of (1 - m*x - sqrt(m^2*x^2 - (2*m+4)*x + 1))/(2*x) are given by a(0)=1 and a(n) = (1/n)*Sum_{k=0..n} (m+1)^k * C(n,k) *C(n,k-1) for n > 0.
Hankel transform is 7^C(n+1,2). - Philippe Deléham, Feb 11 2009
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..200
Paul Barry, On Integer-Sequence-Based Constructions of Generalized Pascal Triangles, Journal of Integer Sequences, Vol. 9 (2006), Article 06.2.4.
FORMULA
a(n) = (1/n)*Sum_{k=0..n} 7^k*C(n, k)*C(n, k-1), a(0)=1.
D-finite with recurrence: (n+1)*a(n) + 8*(1-2*n)*a(n-1) + 36*(n-2)*a(n-2) = 0. - R. J. Mathar, Nov 14 2011
a(n) ~ sqrt(14+8*sqrt(7))*(8+2*sqrt(7))^n*(2*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Oct 14 2012
G.f.: 1/(1 - 6*x - x/(1 - 6*x - x/(1 - 6*x - x/(1 - 6*x - x/(1 - ...))))), a continued fraction. - Ilya Gutkovskiy, Apr 04 2018
MATHEMATICA
Table[SeriesCoefficient[(1-6*x-Sqrt[36*x^2-16*x+1])/(2*x), {x, 0, n}], {n, 0, 20}] (* Vaclav Kotesovec, Oct 14 2012 *)
PROG
(PARI) a(n)=if(n<1, 1, sum(k=0, n, 7^k*binomial(n, k)*binomial(n, k-1))/n)
(PARI) x='x+O('x^99); Vec((1-6*x-(36*x^2-16*x+1)^(1/2))/(2*x)) \\ Altug Alkan, Apr 04 2018
(Magma) m:=30; R<x>:=PowerSeriesRing(Rationals(), m); Coefficients(R!((1-6*x-Sqrt(36*x^2-16*x+1))/(2*x))); // G. C. Greubel, Sep 16 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, May 10 2003
STATUS
approved