A198480 a(n) = 2*7^n - 1.

1, 13, 97, 685, 4801, 33613, 235297, 1647085, 11529601, 80707213, 564950497, 3954653485, 27682574401, 193778020813, 1356446145697, 9495123019885, 66465861139201, 465261027974413, 3256827195820897, 22797790370746285

Offset

0,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (8,-7).

Formula

a(n) = 7*a(n-1)+6, n>0.

G.f.: (1+5*x)/((1-x)*(1-7*x)). - Vincenzo Librandi, Jul 06 2012

a(n) = 8*a(n-1) -7*a(n-2). - Vincenzo Librandi, Jul 06 2012

Mathematica

CoefficientList[Series[(1+5*x)/((1-x)*(1-7*x)), {x, 0, 40}], x] (* Vincenzo Librandi, Jul 06 2012 *)
2*7^Range[0, 20]-1 (* or *) LinearRecurrence[{8, -7}, {1, 13}, 20] (* Harvey P. Dale, Aug 19 2022 *)

Prog

(Magma) [2*7^n-1: n in [0..20]]
(PARI) a(n)=2*7^n-1 \\ Charles R Greathouse IV, Dec 28 2011
(Maxima) A198480(n):=2*7^n-1$ makelist(A198480(n), n, 0, 20); /* Martin Ettl, Nov 09 2012 */

Crossrefs

Cf. A081655, A048473.

Sequence in context: A211388 A125350 A049294 * A126508 A228680 A158795

Adjacent sequences: A198477 A198478 A198479 * A198481 A198482 A198483

Keyword

nonn,easy

Author

Vincenzo Librandi, Oct 27 2011

Status

approved