%I #26 Aug 28 2019 11:52:43
%S 1,1,13,49,277,1321,6733,33409,167557,836761,4185853,20925169,
%T 104634037,523153801,2615801773,13078943329,65394847717,326973976441,
%U 1634870406493,8174350983889,40871757016597,204358780888681,1021793912832013,5108969547382849,25544847770468677
%N a(n) = 3*a(n-1) + 10*a(n-2), n >= 2; a(0)=1, a(1)=1.
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (3,10).
%F a(n) = (4*(-2)^n + 3*5^n)/7.
%F G.f.: (1-2*x)/((1-5*x)*(1+2*x)).
%o (PARI) {a(n) = (4*(-2)^n+3*5^n)/7}
%o (PARI) N=40; x='x+O('x^N); Vec((1-2*x)/((1-5*x)*(1+2*x)))
%Y Cf. A053428, A224473 (trimorphic number), A320468, A321133.
%K nonn,easy
%O 0,3
%A _Seiichi Manyama_, Aug 27 2019