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A136010
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a(0)=20, a(1)=9; for n >= 0, a(n+2) = 7*a(n+1) + 9*a(n).
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1
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20, 9, 243, 1782, 14661, 118665, 962604, 7806213, 63306927, 513404406, 4163593185, 33765791949, 273832882308, 2220722303697, 18009552066651, 146053365199830, 1184459524998669, 9605696961789153, 77900014457512092
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| From an online IQ test (Adaptive IQ).
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FORMULA
| G.f.: (20 - 131*x)/(1-7*x-9*x^2) - M. F. Hasler (www.univ-ag.fr/~mhasler), 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 - A. Povolotsky, simplified by M. F. Hasler, Mar 29 2008
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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
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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 M. Alekseyev, Mar 29 2008
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CROSSREFS
| Sequence in context: A123174 A040384 A078080 * A091534 A033966 A033340
Adjacent sequences: A136007 A136008 A136009 * A136011 A136012 A136013
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KEYWORD
| nonn,easy
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AUTHOR
| Jordan Giedd (jordyg365(AT)gmail.com), Mar 20 2008
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EXTENSIONS
| Definition supplied by Don Reble (djr(AT)nk.ca), Mar 27 2008
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