A113870 a(n) = a(n-1) + 2^(k(n)), where k(n) is the n-th term of the sequence formed by k(1)=0 together with the numbers A042963.

1, 3, 7, 39, 103, 615, 1639, 9831, 26215, 157287, 419431, 2516583, 6710887, 40265319, 107374183, 644245095, 1717986919, 10307921511, 27487790695, 164926744167, 439804651111, 2638827906663, 7036874417767, 42221246506599

Offset

1,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..300

Index entries for linear recurrences with constant coefficients, signature (1, 16, -16).

Formula

G.f.: (3+x-40*x^2)/(4*(-1+x)*(-1+4*x)*(1+4*x)). - Vaclav Kotesovec, Nov 28 2012

Prog

(PARI) a(n)=([0, 1, 0; 0, 0, 1; -16, 16, 1]^(n-1)*[1; 3; 7])[1, 1] \\ Charles R Greathouse IV, Jul 08 2024

Crossrefs

Cf. A099974, A112627, A080355, A080567, A099969, A099970, A099971.

Sequence in context: A061931 A057203 A056250 * A209326 A307952 A074582

Adjacent sequences: A113867 A113868 A113869 * A113871 A113872 A113873

Keyword

nonn,easy

Author

Artur Jasinski, Jan 27 2006

Extensions

Edited with better definition and offset corrected by Omar E. Pol, Jan 08 2009

Status

approved