A247281 a(n) = 4^n -(-1)^n.

0, 5, 15, 65, 255, 1025, 4095, 16385, 65535, 262145, 1048575, 4194305, 16777215, 67108865, 268435455, 1073741825, 4294967295, 17179869185, 68719476735, 274877906945, 1099511627775, 4398046511105, 17592186044415

Offset

0,2

Links

Table of n, a(n) for n=0..22.

OEIS Wiki, Autosequence

Index entries for linear recurrences with constant coefficients, signature (3,4).

Formula

a(n) = 5*A015521(n).

a(n+1) = 10*A037481(n) + 5.

a(n+1) = 4*a(n) + 5*(-1)^n.

a(n) = 3*a(n-1) + 4*a(n-2). - Colin Barker, Sep 11 2014

G.f.: -5*x / ((x+1)*(4*x-1)). - Colin Barker, Sep 11 2014

Mathematica

LinearRecurrence[{3, 4}, {0, 5}, 23] (* Jean-François Alcover, May 22 2016 *)

Prog

(PARI) concat(0, Vec(-5*x / ((x+1)*(4*x-1)) + O(x^100))) \\ Colin Barker, Sep 11 2014
(PARI) vector(100, n, 4^(n-1)+(-1)^n) \\ Derek Orr, Sep 11 2014
(Python)
def A247281(n): return (1<<(n<<1))+(1 if n&1 else -1) # Chai Wah Wu, Jun 28 2023

Crossrefs

Cf. A015521, A037481, A084623.

Sequence in context: A149620 A149621 A149622 * A149623 A149624 A149625

Adjacent sequences: A247278 A247279 A247280 * A247282 A247283 A247284

Keyword

nonn,easy,less

Author

Paul Curtz, Sep 11 2014

Extensions

Typos in data fixed by Colin Barker, Sep 11 2014

Status

approved