A128528 Number of 6-indecomposable (connected) graphs on n nodes.

1, 1, 1, 2, 6, 21, 112, 853, 11117, 261080, 11716571, 1006700565, 164159, 422662, 1295037, 4272969, 12780650, 23303620, 64379033, 189490870, 556338383, 1448500351, 2871171041, 7624849834, 20914847051, 55714746424, 133364472272, 277569288280, 708402263349, 1827946074290, 4530654263579, 10312511072061, 22005420425661, 54057174050076, 132409684714581

Offset

1,4

Comments

See A124593 for definition.

Links

Table of n, a(n) for n=1..35.

Formula

G.f.: x/((1-x)*(1-x^2)^2*(1-x^3)^8*(1-x^4)^44*(1-x^5)^333) + 1 - x^3 - 5*x^4 - 37*x^5 - 295*x^6 + 318*x^7 + 9540*x^8 + 255640*x^9 + 11694624*x^10 + 1006613825*x^11 + 25539*x^12 + 25593*x^13 + 30877*x^14 + 34220*x^15

Crossrefs

Cf. A126099, A128526, A128527

Sequence in context: A076327 A128527 A076328 * A001349 A126060 A266934

Adjacent sequences: A128525 A128526 A128527 * A128529 A128530 A128531

Keyword

nonn

Author

David Applegate and N. J. A. Sloane, Mar 07 2007

Status

approved