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A198769
(9*5^n-1)/4.
1
2, 11, 56, 281, 1406, 7031, 35156, 175781, 878906, 4394531, 21972656, 109863281, 549316406, 2746582031, 13732910156, 68664550781, 343322753906, 1716613769531, 8583068847656, 42915344238281, 214576721191406, 1072883605957031
OFFSET
0,1
FORMULA
a(n) = 5*a(n-1)+1. a(n) = 6*a(n-1)-5*a(n-2), n>1.
G.f.: (2-x)/(5*x^2-6*x+1) [From Harvey P. Dale, May 07 2012]
MATHEMATICA
(9*5^Range[0, 30]-1)/4 (* or *) LinearRecurrence[{6, -5}, {2, 11}, 30] (* Harvey P. Dale, May 07 2012 *)
PROG
(Magma) [(9*5^n-1)/4: n in [0..30]]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Oct 30 2011
STATUS
approved