A086225 a(n) = 11*2^n - 1.

10, 21, 43, 87, 175, 351, 703, 1407, 2815, 5631, 11263, 22527, 45055, 90111, 180223, 360447, 720895, 1441791, 2883583, 5767167, 11534335, 23068671, 46137343, 92274687, 184549375, 369098751, 738197503, 1476395007, 2952790015

Offset

0,1

Comments

(a(n-1))^2 + a(n) is a square. - Vincenzo Librandi, Aug 08 2010

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (3,-2).

Formula

a(n) = 2*a(n-1) + 1.

G.f. ( 10-9*x ) / ( (2*x-1)*(x-1) ). - R. J. Mathar, Oct 22 2011

Mathematica

NestList[2#+1&, 10, 30] (* or *) LinearRecurrence[{3, -2}, {10, 21}, 30] (* Harvey P. Dale, Nov 25 2013 *)

Prog

(PARI) a(n) = 11*2^n - 1 \\ Michel Marcus, Jul 15 2013

Crossrefs

Sequence in context: A192743 A280435 A095824 * A240994 A014007 A074254

Adjacent sequences: A086222 A086223 A086224 * A086226 A086227 A086228

Keyword

nonn,easy

Author

Marco Matosic, Jul 29 2003

Status

approved