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 A180250 a(n) = 5*a(n-1) + 10*a(n-2), with a(1)=0 and a(2)=1. 5
 0, 1, 5, 35, 225, 1475, 9625, 62875, 410625, 2681875, 17515625, 114396875, 747140625, 4879671875, 31869765625, 208145546875, 1359425390625, 8878582421875, 57987166015625, 378721654296875, 2473479931640625, 16154616201171875, 105507880322265625 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Nathaniel Johnston, Table of n, a(n) for n = 1..500 Index entries for linear recurrences with constant coefficients, signature (5, 10). FORMULA a(n) = ((5+sqrt(65))^(n-1) - (5-sqrt(65))^(n-1))/(2^(n-1)*sqrt(65)). - Rolf Pleisch, May 14 2011 G.f.: x^2/(1-5*x-10*x^2). MATHEMATICA Join[{a=0, b=1}, Table[c=5*b+10*a; a=b; b=c, {n, 100}]] LinearRecurrence[{5, 10}, {0, 1}, 30] (* G. C. Greubel, Jan 16 2018 *) PROG (PARI) a(n)=([0, 1; 10, 5]^(n-1))[1, 2] \\ Charles R Greathouse IV, Oct 03 2016 (PARI) x='x+O('x^30); concat9[0], Vec(x^2/(1-5*x-10*x^2))) \\ G. C. Greubel, Jan 16 2018 (MAGMA) I:=[0, 1]; [n le 2 select I[n] else 5*Self(n-1) + 10*Self(n-2): n in [1..30]]; // G. C. Greubel, Jan 16 2018 CROSSREFS Cf. A001076, A006190, A007482, A015520, A015521, A015523, A015524, A015525, A015528, A015529, A015530, A015531, A015532, A015533, A015534, A015535, A015536, A015537, A015440, A015441, A015443, A015444, A015445, A015447, A030195, A053404, A057087, A057088, A083858, A085939, A090017, A091914, A099012, A180222, A180226. Sequence in context: A221578 A320071 A024062 * A002074 A187444 A166176 Adjacent sequences:  A180247 A180248 A180249 * A180251 A180252 A180253 KEYWORD nonn,easy AUTHOR Vladimir Joseph Stephan Orlovsky, Jan 16 2011 STATUS approved

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Last modified May 9 22:46 EDT 2021. Contains 343746 sequences. (Running on oeis4.)