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A136010 a(0)=20, a(1)=9; for n >= 0, a(n+2) = 7*a(n+1) + 9*a(n). 1
20, 9, 243, 1782, 14661, 118665, 962604, 7806213, 63306927, 513404406, 4163593185, 33765791949, 273832882308, 2220722303697, 18009552066651, 146053365199830, 1184459524998669, 9605696961789153, 77900014457512092 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
COMMENTS
From an online IQ test (Adaptive IQ).
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..999 [Offset shifted by Georg Fischer, Jun 18 2021]
FORMULA
G.f.: (20 - 131*x)/(1-7*x-9*x^2). - M. F. Hasler, Mar 27 2008
a(n) = (10 + 61/sqrt(85))*(7/2 - sqrt(85)/2)^n + (10 - 61/sqrt(85))*(7/2 + sqrt(85)/2)^n. - Alexander R. Povolotsky, simplified by M. F. Hasler, Mar 29 2008
MAPLE
A136010:=n -> simplify((10+61/sqrt(85))*(7/2-1/2*sqrt(85))^n+(10-61/sqrt(85))*(7/2+1/2*sqrt(85))^n); # M. F. Hasler, Mar 29 2008
MATHEMATICA
LinearRecurrence[{7, 9}, {20, 9}, 50] (* G. C. Greubel, Feb 21 2017 *)
PROG
(PARI) A136010(n) = { local(y=Mod(x, x^2-85)); lift((10+61/y)*(7/2-1/2*y)^n+(10-61/y)*(7/2+1/2*y)^n)} \\ M. F. Hasler, improved by Max Alekseyev, Mar 29 2008
(PARI) my(x='x+O('x^50)); Vec((20 - 131*x)/(1-7*x-9*x^2)) \\ G. C. Greubel, Feb 21 2017
CROSSREFS
Sequence in context: A040384 A078080 A216289 * A091534 A033966 A033340
KEYWORD
nonn,easy
AUTHOR
Jordan Giedd (jordyg365(AT)gmail.com), Mar 20 2008
EXTENSIONS
Definition supplied by Don Reble, Mar 27 2008
Offset corrected by Georg Fischer, Jun 18 2021
STATUS
approved

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Last modified February 25 19:44 EST 2024. Contains 370332 sequences. (Running on oeis4.)