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A199420
a(n) = (5*7^n+1)/3.
1
2, 12, 82, 572, 4002, 28012, 196082, 1372572, 9608002, 67256012, 470792082, 3295544572, 23068812002, 161481684012, 1130371788082, 7912602516572, 55388217616002, 387717523312012, 2714022663184082, 18998158642288572
OFFSET
0,1
FORMULA
a(n) = 7*a(n-1)-2.
a(n) = 8*a(n-1)-7*a(n-2).
G.f.: 2*(1-2*x)/((1-x)*(1-7*x)).
MATHEMATICA
LinearRecurrence[{8, -7}, {2, 12}, 30] (* Harvey P. Dale, Aug 25 2017 *)
PROG
(Magma) [(5*7^n+1)/3: n in [0..30]];
CROSSREFS
Sequence in context: A340103 A055548 A092850 * A235348 A052864 A355378
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 07 2011
STATUS
approved