%I A137280
%S A137280 1,10,37,181,802,3673,16633,75610,343261,1559053,7079986,32153329,
%T A137280 146019889,663132970,3011538133,13676545189,62110402498,282067023817,
%U A137280 1280973888937,5817390833530,26418989723149,119978705004157
%N A137280 a(n) = 3*a(n-1) + 7*a(n-2).
%C A137280 a(n) == 1 mod 9.
%C A137280 a(n)/a(n-1) tends to 4.54138126... = (3 + sqrt(37))/2
%F A137280 a(1) = 1, a(2) = 10, a(n), n>2 = 3*a(n-1) + 7*a(n-2). a(n) = upper left 
               term in [1,3; 3,2]^n
%F A137280 O.g.f.: x*(1+7*x)/(1-3*x-7*x^2) . a(n)=A015524(n)+7*A015524(n-1). - R. 
               J. Mathar (mathar(AT)strw.leidenuniv.nl), Mar 17 2008
%F A137280 a(n)=-17/74*(3/2-1/2*sqrt(37))^n*sqrt(37)+1/2*(3/2-1/2*sqrt(37))^n+17/
               74*sqrt(37)*(3 /2+1/2*sqrt(37))^n+1/2*(3/2+1/2*sqrt(37))^n, with 
               n>=0 - Paolo P. Lava (ppl(AT)spl.at), Jun 03 2008
%e A137280 a(4) = 181 = 3*a(3) + 7*a(2) = 3*37 + 7*10.
%e A137280 a(4) = 181 = upper left term in [1,3; 3,2]^4.
%Y A137280 Sequence in context: A048480 A116970 A110528 this_sequence A071261 A129426 
               A065009
%Y A137280 Adjacent sequences: A137277 A137278 A137279 this_sequence A137281 A137282 
               A137283
%K A137280 nonn
%O A137280 1,2
%A A137280 Gary W. Adamson (qntmpkt(AT)yahoo.com), Mar 14 2008
%E A137280 More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Mar 17 2008