A091052 Record values in A091023.

1, 2, 13, 26, 205, 410, 3277, 6554, 52429, 104858, 838861, 1677722, 13421773, 26843546, 214748365, 429496730, 3435973837, 6871947674, 54975581389, 109951162778, 879609302221, 1759218604442, 14073748835533, 28147497671066

Offset

1,2

Links

Indranil Ghosh, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (0,17,0,-16)

Formula

Add 1 to every term of A077854, then take the terms with indices 4k and 4k+3.

(1/20) [3*4^n - (-4)^n + 2*(-1)^n + 6]. - Ralf Stephan, Dec 02 2004

G.f. -x*(2*x-1)*(1+2*x)^2 / ( (x-1)*(4*x-1)*(4*x+1)*(1+x) ). - R. J. Mathar, Jun 10 2013

Mathematica

LinearRecurrence[{0, 17, 0, -16}, {1, 2, 13, 26}, 24] (* Indranil Ghosh, Feb 22 2017 *)

Prog

(Python) def A091052(n): return (3*4**n-(-4)**n+2*(-1)**n+6)/20 # Indranil Ghosh, Feb 22 2017
(PARI) a(n)=(3*4^n - (-4)^n + 2*(-1)^n + 6)/20 \\ Charles R Greathouse IV, Feb 22 2017

Crossrefs

Cf. A091023, A091053.

Sequence in context: A367265 A274869 A018400 * A294555 A031090 A358296

Adjacent sequences: A091049 A091050 A091051 * A091053 A091054 A091055

Keyword

nonn,easy

Author

N. J. A. Sloane, Feb 23 2004

Extensions

More terms from David Wasserman, Feb 23 2006

Status

approved