OFFSET
1,1
COMMENTS
The n-web graph is well defined for n >= 3. Sequence extended to n=1 via the number of period n periodic solutions on a larger graph. - Andrew Howroyd, Aug 07 2017
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..200
Eric Weisstein's World of Mathematics, Irredundant Set
Eric Weisstein's World of Mathematics, Web Graph
FORMULA
From Andrew Howroyd, Aug 07 2017: (Start)
Empirical: a(n) = 4*a(n-1) + 3*a(n-2) + 4*a(n-3) + 22*a(n-4) + 12*a(n-5) - 164*a(n-6) + 80*a(n-7) - 24*a(n-8) + 80*a(n-9) for n > 9.
Empirical g.f.: 2*x*(2 + 3*x + 6*x^2 + 44*x^3 + 30*x^4 - 492*x^5 + 280*x^6 - 96*x^7 + 360*x^8)/(1 - 4*x - 3*x^2 - 4*x^3 - 22*x^4 - 12*x^5 + 164*x^6 - 80*x^7 + 24*x^8 - 80*x^9).
(End)
CROSSREFS
KEYWORD
nonn
AUTHOR
Eric W. Weisstein, Aug 07 2017
EXTENSIONS
a(1)-a(2) and terms a(8) and beyond from Andrew Howroyd, Aug 07 2017
STATUS
approved