A072251 (3*a(n)+1)/2^(2*n + 1) = 23-6*n.

15, 45, 117, 213, -171, -4779, -35499, -207531, -1092267, -5417643, -25864875, -120236715, -548055723, -2460658347, -10916375211, -47960468139, -209021741739, -904806443691, -3894103681707, -16675926354603, -71101751929515, -301999193762475, -1278365519227563

Offset

0,1

Comments

Related to the Collatz conjecture.

Links

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

Index entries for linear recurrences with constant coefficients, signature (9, -24, 16).

Formula

a(n) = ((46-12*n)*4^n-1)/3. - Don Reble, Oct 31 2005

a(0)=15, a(1)=45, a(2)=117, a(n)=9*a(n-1)-24*a(n-2)+16*a(n-3). - Harvey P. Dale, Sep 14 2012

G.f.: ( -15+90*x-72*x^2 ) / ( (x-1)*(-1+4*x)^2 ). - R. J. Mathar, Nov 07 2015

Mathematica

Table[((46-12n)4^n-1)/3, {n, 0, 30}] (* or *) LinearRecurrence[{9, -24, 16}, {15, 45, 117}, 40] (* Harvey P. Dale, Sep 14 2012 *)

Crossrefs

Sequence in context: A278337 A270563 A126228 * A002756 A039450 A127069

Adjacent sequences: A072248 A072249 A072250 * A072252 A072253 A072254

Keyword

sign,easy,less

Author

N. Rathankar (rathankar(AT)yahoo.com), Jul 08 2002

Extensions

Edited and extended by David Wasserman, Dec 27 2006

Corrected by N. J. A. Sloane, Mar 01 2007

Status

approved