Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #16 Apr 11 2023 13:32:34
%S 3,19,139,1099,9043,76099,649819,5608699,48818083,427793779,
%T 3769318699,33358563499,296271355123,2638756433059,23555020310779,
%U 210638707953499,1886253162468163,16909812342793939,151723049282330059
%N a(n) = 3^n + 7^n + 9^n.
%H Vincenzo Librandi, <a href="/A074559/b074559.txt">Table of n, a(n) for n = 0..1000</a>
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (19,-111,189).
%F From _Mohammad K. Azarian_, Dec 30 2008: (Start)
%F G.f.: 1/(1-3*x) + 1/(1-7*x) + 1/(1-9*x).
%F E.g.f.: exp(3*x) + exp(7*x) + exp(9*x). (End)
%F a(n) = 19*a(n-1) - 111*a(n-2) + 189*a(n-3). - _Wesley Ivan Hurt_, Apr 11 2023
%t Table[3^n + 7^n + 9^n, {n, 0, 20}]
%o (Magma) [3^n + 7^n + 9^n: n in [0..20]]; // _Vincenzo Librandi_, Aug 24 2011
%Y Cf. A001550, A001576, A034513, A001579, A074501 - A074580.
%K easy,nonn
%O 0,1
%A _Robert G. Wilson v_, Aug 23 2002