OFFSET
2,1
LINKS
Andrew Howroyd, Table of n, a(n) for n = 2..1000
Eric Weisstein's World of Mathematics, Crossed Prism Graph
Eric Weisstein's World of Mathematics, Minimum Dominating Set
Index entries for linear recurrences with constant coefficients, signature (0,4,0,-4).
FORMULA
a(n) = 2^((n/2)+1) for n even.
From Andrew Howroyd, Jan 18 2022: (Start)
a(n) = 17*n*2^((n-3)/2) for n odd.
a(n) = 4*a(n-2) - 4*a(n-4) for n > 5.
G.f.: x^2*(4 + 51*x - 8*x^2 - 34*x^3)/(1 - 2*x^2)^2.
(End)
MATHEMATICA
Table[Piecewise[{{17 n 2^((n - 3)/2), Mod[n, 2] == 1}, {2^((n/2) + 1), Mod[n, 2] == 0}}], {n, 2, 20}] (* Eric W. Weisstein, Feb 27 2025 *)
CoefficientList[Series[(4 + 51 x - 8 x^2 - 34 x^3)/(1 - 2 x^2)^2, {x, 0, 20}], x] (* Eric W. Weisstein, Feb 27 2025 *)
PROG
(PARI) a(n) = if(n%2, 17*n*2^((n-3)/2), 2^((n/2)+1)) \\ Andrew Howroyd, Jan 18 2022
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Eric W. Weisstein, Sep 06 2021
EXTENSIONS
Terms a(11) and beyond from Andrew Howroyd, Jan 18 2022
STATUS
approved