OFFSET
1,2
LINKS
E. S. Egge, Restricted 3412-Avoiding Involutions: Continued Fractions, Chebyshev Polynomials and Enumerations, sec. 8
Index entries for linear recurrences with constant coefficients, signature (3,-1,-5,5,1,-3,1).
FORMULA
a(n) = (2*n^4-4*n^3+28*n^2-2*n+81-6*n*(-1)^n+15*(-1)^n)/96.
G.f.: -x*(x^6-2*x^5+x^4+3*x^3-x^2-x+1) / ((x-1)^5*(x+1)^2). - Colin Barker, Jul 16 2013
a(n) = 3*a(n-1) - a(n-2) - 5*a(n-3) + 5*a(n-4) + a(n-5) - 3*a(n-6) + a(n-7). - Wesley Ivan Hurt, Jan 20 2024
MATHEMATICA
CoefficientList[Series[-(x^6 - 2*x^5 + x^4 + 3*x^3 - x^2 - x + 1)/((x - 1)^5*(x + 1)^2), {x, 0, 50}], x] (* Wesley Ivan Hurt, Jan 20 2024 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Ralf Stephan, Jul 06 2003
EXTENSIONS
More terms from Colin Barker, Jul 16 2013
STATUS
approved