OFFSET
1,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..5000
Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,1,-1).
FORMULA
G.f.: x^2*(2+x+x^2+x^3+x^4) / ( (x^4+x^3+x^2+x+1)*(x-1)^2 ). - R. J. Mathar, Oct 08 2011
Sum_{n>=2} (-1)^n/a(n) = log(2+sqrt(3))/(2*sqrt(3)) + log(2)/6 - (9-4*sqrt(3))*Pi/36. - Amiram Eldar, Dec 17 2021
MATHEMATICA
Rest[CoefficientList[Series[x^2*(2 + x + x^2 + x^3 + x^4)/((x^4 + x^3 + x^2 + x + 1)*(x - 1)^2), {x, 0, 50}], x]] (* G. C. Greubel, Nov 02 2017 *)
DeleteCases[Range[0, 70], _?(Mod[#, 6]==1&)] (* or *) Complement[ Range[ 0, 70], Range[1, 70, 6]] (* Harvey P. Dale, Dec 30 2017 *)
PROG
(PARI) x='x+O('x^50); concat([0], Vec(x^2*(2+x+x^2+x^3+x^4)/((x^4 +x^3 +x^2 +x+1)*(x-1)^2))) \\ G. C. Greubel, Nov 02 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved