A177123 Sequence defined by the recurrence formula a(n+1)=sum(a(p)*a(n-p)+k,p=0..n)+l for n>=1, with here a(0)=1, a(1)=7, k=1 and l=1.

1, 7, 17, 87, 417, 2347, 13497, 81607, 504537, 3192747, 20529537, 133876327, 882924177, 5879675307, 39478170697, 266973261127, 1816729697097, 12431013514667, 85476914070417, 590327766229607, 4093067887259777

Offset

0,2

Comments

To see by recurrence: a(n)=7 mod10 for n>0.

Links

Table of n, a(n) for n=0..20.

Formula

G.f f: f(z)=(1-sqrt(1-4*z*(a(0)-z*a(0)^2+z*a(1)+(k+l)*z^2/(1-z)+k*z^2/(1-z)^2)))/(2*z) (k=1, l=1).

Conjecture: +(n+1)*a(n) +(-7*n+2)*a(n-1) +9*(-n+3)*a(n-2) +(47*n-142)*a(n-3) +48*(-n+4)*a(n-4) +16*(n-5)*a(n-5)=0. - R. J. Mathar, Mar 02 2016

Example

a(2)=2*1*7+2+1=17. a(3)=2*1*17+2+7^2+1+1=87. a(4)=2*1*87+2+2*7*17+2+1=417.

Maple

l:=1: : k := 1 : m :=7: d(0):=1:d(1):=m: for n from 1 to 32 do d(n+1):=sum(d(p)*d(n-p)+k, p=0..n)+l:od :
taylor((1-sqrt(1-4*z*(d(0)-z*d(0)^2+z*m+(k+l)*z^2/(1-z)+k*z^2/(1-z)^2)))/(2*z), z=0, 34); seq(d(n), n=0..32);

Crossrefs

Cf. A177122.

Sequence in context: A123206 A035078 A359015 * A124165 A239150 A092057

Adjacent sequences: A177120 A177121 A177122 * A177124 A177125 A177126

Keyword

easy,nonn

Author

Richard Choulet, May 03 2010

Status

approved