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A199215
a(n) = 4*5^n+1.
1
5, 21, 101, 501, 2501, 12501, 62501, 312501, 1562501, 7812501, 39062501, 195312501, 976562501, 4882812501, 24414062501, 122070312501, 610351562501, 3051757812501, 15258789062501, 76293945312501, 381469726562501, 1907348632812501
OFFSET
0,1
FORMULA
a(n) = 5*a(n-1)-4.
a(n) = 6*a(n-1)-5*a(n-2).
G.f.: (5-9*x)/((1-x)*(1-5*x)). - Bruno Berselli, Nov 04 2011
MATHEMATICA
4*5^Range[0, 30]+1 (* or *) LinearRecurrence[{6, -5}, {5, 21}, 30] (* Harvey P. Dale, Mar 30 2018 *)
PROG
(Magma) [4*5^n+1: n in [0..30]];
CROSSREFS
Sequence in context: A017969 A050897 A338673 * A204061 A362556 A046633
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 04 2011
STATUS
approved