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A198767
8*5^n-1.
1
7, 39, 199, 999, 4999, 24999, 124999, 624999, 3124999, 15624999, 78124999, 390624999, 1953124999, 9765624999, 48828124999, 244140624999, 1220703124999, 6103515624999, 30517578124999, 152587890624999, 762939453124999
OFFSET
0,1
FORMULA
a(n) = 5*a(n-1)+4.
a(n) = 6*a(n-1)-5*a(n-2), n>1.
G.f.: (7 - 3*x)/(1 - 6*x + 5*x^2). - Vincenzo Librandi, Jan 04 2013
MATHEMATICA
CoefficientList[Series[(7 - 3*x)/(1 - 6*x + 5*x^2), {x, 0, 30}], x] (* Vincenzo Librandi, Jan 04 2013 *)
PROG
(Magma) [8*5^n-1: n in [0..30]];
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Oct 30 2011
STATUS
approved