A087231 a(n) is the smallest number such that the exponent of p=2 factor in 6*a(n)+4 equals n.

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

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