OFFSET
0,2
COMMENTS
The denominator is a parameterization of the Alexander polynomial for the knot 8_12. The g.f. is the image of the g.f. of A099453 under the Chebyshev transform A(x)->(1/(1+x^2))A(x/(1+x^2)).
LINKS
Stefano Spezia, Table of n, a(n) for n = 0..1500
Dror Bar-Natan, The Rolfsen Knot Table.
Index entries for linear recurrences with constant coefficients, signature (7,-13,7,-1).
FORMULA
G.f.: (1+x^2)/(1-7x+13x^2-7x^3+x^4).
a(n) = Sum_{k=0..floor(n/2)} C(n-k, k)*(-1)^k*Sum{j=0..n-2*k} C(n-2*k-j, j)*(-11)^j*7^(n-2*k-2*j).
a(n) = Sum_{k=0..floor(n/2)} C(n-k, k)*(-1)^k*A099453(n-2*k)).
a(n) = Sum_{k=0..n} binomial((n+k)/2, k)*(-1)^((n-k)/2)*(1+(-1)^(n+k))*A099453(k)/2.
a(n) = Sum_{k=0..n} A099455(n-k)*binomial(1, k/2)*(1+(-1)^k)/2.
MATHEMATICA
CoefficientList[Series[(1+x^2)/(1-7x+13x^2-7x^3+x^4), {x, 0, 24}], x] (* Stefano Spezia, May 13 2024 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Oct 16 2004
STATUS
approved