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A143079 a(n) = ((9+sqrt(9))^n + (9-sqrt(9))^n)/2. 7
1, 9, 90, 972, 11016, 128304, 1516320, 18055872, 215830656, 2584929024, 30988915200, 371685583872, 4459138615296, 53503133036544, 641998414356480, 7703745879785472, 92443540002471936, 1109314016699940864 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Equals A007318^9 * [1, 0, 9, 0, 81, 0, 729,...]. - Gary W. Adamson, Oct 23 2008

LINKS

Table of n, a(n) for n=0..17.

FORMULA

a(n)=18*a(n-1)-72*a(n-2). a(n)=6^n*(2^n+1)/2 . G.f.:(1-9x)/(1-18x+72x^2). - Philippe Deléham, Oct 18 2008

a(n)=(12^n+6^n)/2. G.f.: (1-9x)/((1-12x)(1-6x)). - R. J. Mathar, Oct 21 2008

a(n) = 3^n*A007582(n) = (6^n+12^n)/2 = A000051(n)*A000079(n)*A000244(n)/2. - M. F. Hasler, Oct 22 2008

A007318^9 * [1, 0, 9, 0, 81, 0, 729...] produces this sequence. - Gary W. Adamson, Oct 23 2008

a(n)=Sum_{k, 0<=k<=n}A098158(n,k)*9^k. - Philippe Deléham, Oct 23 2008

EXAMPLE

a(3)=972

PROG

(PARI) A143079(n)=3^n*(1+1<<n)<<(n-1) \\ M. F. Hasler, Oct 22 2008

CROSSREFS

Sequence in context: A036258 A098399 A264914 * A233829 A165324 A082367

Adjacent sequences:  A143076 A143077 A143078 * A143080 A143081 A143082

KEYWORD

nonn

AUTHOR

Al Hakanson (hawkuu(AT)gmail.com), Oct 15 2008

EXTENSIONS

Extended by R. J. Mathar and M. F. Hasler, Oct 21 2008

STATUS

approved

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Last modified April 1 02:24 EDT 2020. Contains 333153 sequences. (Running on oeis4.)