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 A076184 Graph code numbers of simple graphs in numerical order. 1
 0, 1, 3, 7, 11, 12, 13, 15, 30, 31, 63, 75, 76, 77, 79, 86, 87, 94, 95, 116, 117, 119, 127, 222, 223, 235, 236, 237, 239, 254, 255, 507, 511, 1023, 1099, 1100, 1101, 1103, 1108, 1109, 1110, 1111, 1118, 1119, 1140, 1141, 1143, 1151, 1182, 1183, 1184, 1185, 1187 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Every simple graph has a symmetric adjacency matrix whose lower triangular part by rows represents a little-endian binary number of which the minimum value over all isomorphic graphs gives the graph code number. Adding isolated vertices will not change the graph code number. Study of the patterns and gaps in the sequence appears to be quite interesting. The number of terms that are less than 2^(n*(n-1)/2) is equal to A000088(n). - Vladimir Kulipanov, Oct 13 2015 REFERENCES F. Harary, Problems involving graphical numbers, in Colloq. Math. Soc. Janos Bolyai, 4 (1970) 625-635. Look at his 'mincode numbers'. K. R. Parthasarathy, Graph Code Numbers, preprint. LINKS Table of n, a(n) for n=1..53. Vladimir Kulipanov, Table of n, a(n) for n = 1..156 EXAMPLE a(5)=11 in binary (with 0's prepended to give a triangular number of digits) is 001011 so adjacency matrix [0,1,1,1; 1,0,0,0; 1,0,0,0; 1,0,0,0]. a(6)=12 in binary is 001100 so adjacency matrix [0,0,0,1; 0,0,1,0; 0,1,0,0; 1,0,0,0]. CROSSREFS Cf. A000088. Sequence in context: A337250 A043345 A023718 * A310191 A135137 A263737 Adjacent sequences: A076181 A076182 A076183 * A076185 A076186 A076187 KEYWORD nonn AUTHOR K. R. Parthasarathy (nuns(AT)vsnl.com), Nov 02 2002 STATUS approved

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Last modified September 17 08:52 EDT 2024. Contains 375987 sequences. (Running on oeis4.)