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A199489
(11*7^n+1)/6.
1
2, 13, 90, 629, 4402, 30813, 215690, 1509829, 10568802, 73981613, 517871290, 3625099029, 25375693202, 177629852413, 1243408966890, 8703862768229, 60927039377602, 426489275643213, 2985424929502490, 20897974506517429
OFFSET
0,1
FORMULA
a(n) = 7*a(n-1)-1.
a(n) = 8*a(n-1)-7*a(n-2).
G.f.: (2-3*x)/((1-x)*(1-7*x)).
MATHEMATICA
(11*7^Range[0, 20]+1)/6 (* or *) LinearRecurrence[{8, -7}, {2, 13}, 20] (* Harvey P. Dale, May 05 2019 *)
PROG
(Magma) [(11*7^n+1)/6: n in [0..30]];
CROSSREFS
Sequence in context: A074617 A337169 A367785 * A300764 A381147 A209470
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 07 2011
STATUS
approved