OFFSET
1,3
COMMENTS
For n > 2, the minimum total dominating sets are any three vertices such that no two are in the same row or column. - Andrew Howroyd, Apr 20 2018
Essentially the same as A179058(n), differing only for n=2. - Eric W. Weisstein, Dec 06 2023
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Eric Weisstein's World of Mathematics, Rook Complement Graph.
Eric Weisstein's World of Mathematics, Total Dominating Set.
Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1).
FORMULA
a(n) = A179058(n) for n > 2. - Andrew Howroyd, Apr 20 2018
From Colin Barker, Apr 20 2018: (Start)
G.f.: x^2*(1 - x + 75*x^2 + 19*x^3 + 41*x^4 - 21*x^5 + 7*x^6 - x^7) / (1 - x)^7.
a(n) = n^2*(2 - 3*n + n^2)^2 / 6 for n > 2.
a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n > 9.
(End)
MATHEMATICA
Table[If[n == 2, 1, 6 Binomial[n, 3]^2], {n, 20}]
Join[{0, 1}, LinearRecurrence[{7, -21, 35, -35, 21, -7, 1}, {0, 0, 6, 96, 600, 2400, 7350}, {3, 20}]]
CoefficientList[Series[x (-1 + x - 75 x^2 - 19 x^3 - 41 x^4 + 21 x^5 - 7 x^6 + x^7)/(-1 + x)^7, {x, 0, 20}], x]
PROG
(PARI) a(n) = if(n<3, n==2, 6*binomial(n, 3)^2) \\ Andrew Howroyd, Apr 20 2018
(PARI) concat(0, Vec(x^2*(1 - x + 75*x^2 + 19*x^3 + 41*x^4 - 21*x^5 + 7*x^6 - x^7) / (1 - x)^7 + O(x^60))) \\ Colin Barker, Apr 20 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Eric W. Weisstein, Apr 19 2018
EXTENSIONS
a(6)-a(30) from Andrew Howroyd, Apr 20 2018
STATUS
approved