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A074543
a(n) = 2^n + 6^n + 9^n.
1
3, 17, 121, 953, 7873, 66857, 578161, 5063033, 44726593, 397498697, 3547251601, 31743858713, 284606322913, 2554926530537, 22955156635441, 206361317111993, 1855841298824833, 16694108359242377, 150196195253929681
OFFSET
0,1
FORMULA
From Mohammad K. Azarian, Dec 27 2008: (Start)
G.f.: 1/(1-2*x) + 1/(1-6*x) + 1/(1-9*x).
E.g.f.: exp(2*x) + exp(6*x) + exp(9*x). (End)
a(n) = 17*a(n-1) - 84*a(n-2) + 108*a(n-3); a(0)=3, a(1)=17, a(2)=121. - Harvey P. Dale, Feb 20 2015
MATHEMATICA
Table[2^n + 6^n + 9^n, {n, 0, 20}]
LinearRecurrence[{17, -84, 108}, {3, 17, 121}, 30] (* Harvey P. Dale, Feb 20 2015 *)
PROG
(Magma) [2^n + 6^n + 9^n: n in [0..20]]; // Vincenzo Librandi, Jun 11 2011
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Robert G. Wilson v, Aug 23 2002
STATUS
approved