A006627 Number of nonisomorphic 2-graphs with n nodes with first and second cohomology invariants both 0.

1, 1, 2, 3, 7, 14, 54, 224, 2038, 32728

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• nice

References

• Buekenhout, ed., Handbook of Incidence Geometry, 1995, p. 884.
• J. J. Seidel and D. E. Taylor, Two-graphs: a second survey, pp. 689-711 of L. Lovasz and V. Sos, eds., Algebraic Methods in Graph Theory (Colloq. Janos Bolyai 25), North-Holland, 1981.
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• F. C. Bussemaker, R. A. Mathon and J. J. Seidel, Tables of two-graphs, T.H.-Report 79-WSK-05, Technological University Eindhoven, Dept. Mathematics, 1979; also pp. 71-112 of "Combinatorics and Graph Theory (Calcutta, 1980)", Lect. Notes Math. 885, 1981.
• F. C. Bussemaker, R. A. Mathon and J. J. Seidel, Tables of two-graphs, T.H.-Report 79-WSK-05, Technological University Eindhoven, Dept. Mathematics, 1979; also pp. 71-112 of "Combinatorics and Graph Theory (Calcutta, 1980)", Lect. Notes Math. 885, 1981.

Crossrefs

Cf. A085617, A002854.