A152106 - OEIS

A152106

a(n) = (11^n + 7^n)/2.

1, 9, 85, 837, 8521, 88929, 944605, 10155357, 110061841, 1199150649, 13109949925, 143644498677, 1576134831961, 17309800577169, 190214028328045, 2090997865462797, 22991481397070881, 252839829506640489, 2780772863545070965, 30585244671799959717, 336414893599428810601

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,2

LINKS

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

Index entries for linear recurrences with constant coefficients, signature (18,-77).

FORMULA

a(n) = ((9 + sqrt(4))^n + (9 - sqrt(4))^n)/2.

From Philippe Deléham, Nov 26 2008: (Start)

a(n) = 18*a(n-1) - 77*a(n-2), n > 1; a(0)=1, a(1)=9.

G.f.: (1-9*x)/(1-18*x+77*x^2).

a(n) = (1/9^n)*Sum_{k=0..n} A098158(n,k)*9^(2*k)*4^(n-k). (End)