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A199412
a(n) = (9*6^n+1)/5.
2
2, 11, 65, 389, 2333, 13997, 83981, 503885, 3023309, 18139853, 108839117, 653034701, 3918208205, 23509249229, 141055495373, 846332972237, 5077997833421, 30467987000525, 182807922003149, 1096847532018893, 6581085192113357, 39486511152680141
OFFSET
0,1
FORMULA
a(n) = 6*a(n-1)-1.
a(n) = 7*a(n-1)-6*a(n-2).
G.f.: (2-3*x)/((1-x)*(1-6*x)).
PROG
(Magma) [(9*6^n+1)/5: n in [0..30]];
CROSSREFS
Sequence in context: A349023 A001565 A357845 * A074613 A247109 A039632
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 06 2011
STATUS
approved