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A199421
(5*7^n+1)/2.
1
3, 18, 123, 858, 6003, 42018, 294123, 2058858, 14412003, 100884018, 706188123, 4943316858, 34603218003, 242222526018, 1695557682123, 11868903774858, 83082326424003, 581576284968018, 4071033994776123, 28497237963432858
OFFSET
0,1
FORMULA
a(n) = 7*a(n-1)-3.
a(n) = 8*a(n-1)-7*a(n-2).
G.f.: 3*(1-2*x)/((1-x)*(1-7*x)).
PROG
(Magma) [(5*7^n+1)/2: n in [0..30]];
CROSSREFS
Sequence in context: A074564 A108241 A342710 * A305869 A371483 A181998
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Nov 07 2011
STATUS
approved