A155559 a(n) = 2*A131577(n).

0, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 67108864, 134217728, 268435456, 536870912, 1073741824, 2147483648, 4294967296, 8589934592

Offset: 0

Author

Paul Curtz, Jan 24 2009

Keywords

• nonn
• easy
• changed

Comments

Essentially the same as A131577, A046055, A011782, A000079 and A034008.

Links

• Index entries for linear recurrences with constant coefficients, signature (2).

Crossrefs

Cf. A000079, A007582, A011782, A034008, A046055, A063376, A084633, A090129, A131577, A137173.

Programs

Mathematica

CoefficientList[ Series[ 2x/(1 - 2x), {x, 0, 32}], x] (* Robert G. Wilson v, Aug 08 2018 *)

PARI

a(n)=if(n,2^n,0) \\ Charles R Greathouse IV, Aug 01 2016

Python

def A155559(n): return 1<Chai Wah Wu, Sep 05 2024

Formula

a(n) = A000079(n), n>0.

a(n) = (-1)^(n+1)*A084633(n+1).

a(n) + A155543(n) = 2^n+4^n = A063376(n) = 2*A007582(n) =2*A137173(2n+1).

Conjecture: a(n) = A090129(n+3)-A090129(n+2).

G.f.: 2*x/(1-2*x). - R. J. Mathar, Jul 23 2009

E.g.f.: exp(2*x) - 1. - Stefano Spezia, Aug 26 2025

Extensions

Edited by R. J. Mathar, Jul 23 2009

Extended by Omar E. Pol, Nov 19 2012