A290591 Number of irredundant sets in the n-web graph.

4, 22, 112, 618, 3044, 14026, 70340, 347074, 1713820, 8430362, 41516292, 204628626, 1008216460, 4967464650, 24473678612, 120581823170, 594106884060, 2927147525626, 14421969381220, 71056635221618, 350094259434668, 1724905262555178, 8498562511858612

Offset: 1

Author

Eric W. Weisstein, Aug 07 2017

Keywords

• nonn

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

Crossrefs

Cf. A287474, A290381.

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)

Extensions

a(1)-a(2) and terms a(8) and beyond from Andrew Howroyd, Aug 07 2017