OFFSET
1,1
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..200
Eric Weisstein's World of Mathematics, Dipyramidal Graph
Eric Weisstein's World of Mathematics, Total Dominating Set
Index entries for linear recurrences with constant coefficients, signature (2,-1,1,-1,0,0,-1,0,1,1,-1).
FORMULA
From Andrew Howroyd, Jun 26 2018: (Start)
a(n) = 2*a(n-1) - a(n-2) + a(n-3) - a(n-4) - a(n-7) + a(n-9) + a(n-10) - a(n-11) for n > 11.
G.f.: x*(2 + 3*x^2 - 4*x^3 - 2*x^4 - 2*x^5 - 9*x^6 - 2*x^7 + 9*x^8 + 12*x^9 - 9*x^10)/((1 - x)^2*(1 - x^2 - x^3)*(1 + x^2 - x^6)). (End)
MATHEMATICA
Table[2 n + RootSum[-1 - # + #^3 &, #^n &] + (1 + (-1)^n) RootSum[-1 - # + #^3 &, #^(-n/2) &], {n, 20}]
LinearRecurrence[{2, -1, 1, -1, 0, 0, -1, 0, 1, 1, -1}, {2, 4, 9, 12, 15, 21, 21, 20, 30, 45, 44}, 20]
CoefficientList[Series[(2 + 3 x^2 - 4 x^3 - 2 x^4 - 2 x^5 - 9 x^6 - 2 x^7 + 9 x^8 + 12 x^9 - 9 x^10)/((-1 + x)^2 (1 - x^3 - x^4 - x^5 - x^6 + x^8 + x^9)), {x, 0, 20}], x]
PROG
(PARI) Vec((2 + 3*x^2 - 4*x^3 - 2*x^4 - 2*x^5 - 9*x^6 - 2*x^7 + 9*x^8 + 12*x^9 - 9*x^10)/((1 - x)^2*(1 - x^2 - x^3)*(1 + x^2 - x^6)) + O(x^50)) \\ Andrew Howroyd, Jun 26 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Eric W. Weisstein, Jun 18 2018
EXTENSIONS
a(1)-a(2) and terms a(21) and beyond from Andrew Howroyd, Jun 26 2018
STATUS
approved