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A199491
(11*7^n+1)/2.
1
6, 39, 270, 1887, 13206, 92439, 647070, 4529487, 31706406, 221944839, 1553613870, 10875297087, 76127079606, 532889557239, 3730226900670, 26111588304687, 182781118132806, 1279467826929639, 8956274788507470, 62693923519552287
OFFSET
0,1
FORMULA
a(n) = 7*a(n-1)-3.
a(n) = 8*a(n-1)-7*a(n-2).
G.f.: 3*(2-3*x)/((1-x)*(1-7*x)).
MATHEMATICA
(11*7^Range[0, 30]+1)/2 (* or *) LinearRecurrence[{8, -7}, {6, 39}, 30] (* Harvey P. Dale, Jan 23 2013 *)
PROG
(Magma) [(11*7^n+1)/2: n in [0..30]];
CROSSREFS
Sequence in context: A370376 A357206 A370026 * A147961 A264232 A372536
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 07 2011
STATUS
approved