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A007751 Even bisection of A007750. 2
0, 7, 120, 1921, 30624, 488071, 7778520, 123968257, 1975713600, 31487449351, 501823476024, 7997688167041, 127461187196640, 2031381306979207, 32374639724470680, 515962854284551681, 8223031028828356224 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

REFERENCES

Mentioned in a problem on p. 334 of Two-Year College Math. Jnl., Vol. 25, 1994.

LINKS

Table of n, a(n) for n=0..16.

FORMULA

G.f.: x(7+x)/((1-x)(1-16x+x^2)). a(n)=16a(n-1)-a(n-2)+8.

a(n)=-4/7+(2/7)*[8-3*sqrt(7)]^n+(2/7)*[8+3*sqrt(7)]^n+(1/14)*sqrt(7)*[8+3*sqrt(7)]^n-(1/14) *[8-3*sqrt(7)]^n*sqrt(7), with n>=0 - Paolo P. Lava, Jun 19 2008

PROG

(PARI) a(n)=local(w); w=8+3*quadgen(28); imag(w^n)+4*(real(w^n)-1)/7

CROSSREFS

Cf. A007750, A007752.

Sequence in context: A092612 A263943 A302718 * A193785 A253276 A156955

Adjacent sequences:  A007748 A007749 A007750 * A007752 A007753 A007754

KEYWORD

nonn

AUTHOR

John C. Hallyburton, Jr. [ hallyb(AT)vmsdev.enet.dec.com ].

EXTENSIONS

Edited by Michael Somos, Jul 27, 2002

STATUS

approved

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Last modified July 19 03:54 EDT 2019. Contains 325144 sequences. (Running on oeis4.)