OFFSET
0,2
COMMENTS
a(n)/a(n-1) tends to (15+sqrt(29))/2=10,192582...
For n>=2, a(n) equals 7^n times the permanent of the (2n-2)X(2n-2) tridiagonal matrix with 1/sqrt(7)'s along the main diagonal, and 1's along the superdiagonal and the subdiagonal. [John M. Campbell,Jul 08 2011]
LINKS
FORMULA
G.f.: (1-8x)/(1-15x+49x^2).
a(n) = Sum_{k=0..n}A165253(n,k)*7^(n-k).
a(n) = ((29-sqrt(29))*(15+sqrt(29))^n+(29+sqrt(29))*(15-sqrt(29))^n )/(58*2^n). [Klaus Brockhaus,Sep 26 2009]
MATHEMATICA
LinearRecurrence[{15, -49}, {1, 7}, 20] (*Harvey P. Dale,Jun 04 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Philippe Deléham,Sep 14 2009
STATUS
approved