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 A087231 a(n) is the smallest number such that the exponent of p=2 factor in 6*a(n)+4 equals n. 2
 1, 4, 6, 2, 26, 10, 106, 42, 426, 170, 1706, 682, 6826, 2730, 27306, 10922, 109226, 43690, 436906, 174762, 1747626, 699050, 6990506, 2796202, 27962026, 11184810, 111848106, 44739242, 447392426, 178956970, 1789569706, 715827882, 7158278826, 2863311530 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Colin Barker, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (1,4,-4) FORMULA For n>2, a(n) = [3/2*2^n - (-2)^n - 2]/3. - Ralf Stephan, May 10 2004 From Colin Barker, Mar 16 2017: (Start) G.f.: x*(1 + 3*x - 2*x^2 - 16*x^3 + 16*x^4) / ((1 - x)*(1 - 2*x)*(1 + 2*x)). a(n) = a(n-1) + 4*a(n-2) - 4*a(n-3) for n>5. (End) EXAMPLE n = 10: m = 6*170+4 = 1024 = 2^10, so a(10) = 170. PROG (PARI) Vec(x*(1 + 3*x - 2*x^2 - 16*x^3 + 16*x^4) / ((1 - x)*(1 - 2*x)*(1 + 2*x)) + O(x^40)) \\ Colin Barker, Mar 16 2017 CROSSREFS Cf. A085058, A087229, A087230. Sequence in context: A173458 A054222 A066891 * A019211 A212084 A182368 Adjacent sequences:  A087228 A087229 A087230 * A087232 A087233 A087234 KEYWORD nonn,easy AUTHOR Labos Elemer, Aug 28 2003 STATUS approved

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Last modified January 29 11:16 EST 2020. Contains 331337 sequences. (Running on oeis4.)