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 A123551 Triangle read by rows: T(n,k) gives number of unlabeled graphs without endpoints on n nodes and k edges, (n >= 0, 0 <= k <= n(n-1)/2). 2
 1, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 2, 4, 3, 2, 1, 1, 1, 0, 0, 1, 1, 2, 6, 8, 13, 16, 13, 8, 5, 2, 1, 1, 1, 0, 0, 1, 1, 2, 6, 10, 22, 48, 76, 97, 102, 84, 60, 39, 20, 10, 5, 2, 1, 1, 1, 0, 0, 1, 1, 2, 6, 10, 25, 64, 152, 331, 617, 930, 1173, 1253, 1140 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,21 REFERENCES R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1977. LINKS R. W. Robinson, Rows 0 through 16, flattened FORMULA T(n,k) = A008406(n,k) - A240168(n,k). - Andrew Howroyd, Apr 16 2021 EXAMPLE Triangle begins: n = 0 k = 0 : 1 ******************** total (n = 0) = 1 n = 1 k = 0 : 1 ******************** total (n = 1) = 1 n = 2 k = 0 : 1 k = 1 : 0 ******************** total (n = 2) = 1 n = 3 k = 0 : 1 k = 1 : 0 k = 2 : 0 k = 3 : 1 ******************** total (n = 3) = 2 n = 4 k = 0 : 1 k = 1 : 0 k = 2 : 0 k = 3 : 1 k = 4 : 1 k = 5 : 1 k = 6 : 1 ******************** total (n = 4) = 5 CROSSREFS Row sums are A004110. Cf. A008406, A240168. Sequence in context: A307500 A049245 A123547 * A286275 A029717 A135567 Adjacent sequences: A123548 A123549 A123550 * A123552 A123553 A123554 KEYWORD nonn,tabf AUTHOR N. J. A. Sloane, Nov 14 2006 STATUS approved

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Last modified February 7 15:43 EST 2023. Contains 360127 sequences. (Running on oeis4.)