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A198480 a(n) = 2*7^n - 1. 10
1, 13, 97, 685, 4801, 33613, 235297, 1647085, 11529601, 80707213, 564950497, 3954653485, 27682574401, 193778020813, 1356446145697, 9495123019885, 66465861139201, 465261027974413, 3256827195820897, 22797790370746285 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
LINKS
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
Sequence in context: A211388 A125350 A049294 * A126508 A228680 A372770
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Oct 27 2011
STATUS
approved

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Last modified July 19 10:10 EDT 2024. Contains 374392 sequences. (Running on oeis4.)