
LINKS

Table of n, a(n) for n=4..9.
F. C. Bussemaker, R. A. Mathon and J. J. Seidel, Tables of twographs, T.H.Report 79WSK05, Technological University Eindhoven, Dept. Mathematics, 1979; also pp. 71112 of "Combinatorics and Graph Theory (Calcutta, 1980)", Lect. Notes Math. 885, 1981.
F. C. Bussemaker, R. A. Mathon and J. J. Seidel, Tables of twographs, T.H.Report 79WSK05, Technological University Eindhoven, Dept. Mathematics, 1979; also pp. 71112 of "Combinatorics and Graph Theory (Calcutta, 1980)", Lect. Notes Math. 885, 1981.
Tadeusz Sozański, Enumeration of weak isomorphism classes of signed graphs, J. Graph Theory 4 (1980), no. 2, 127144.
