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 A008326 Triangle read by rows: T(n,k) is the number of simple regular connected bipartite graphs with 2n nodes and degree k, (2 <= k <= n). 8
 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 5, 4, 1, 1, 1, 13, 14, 4, 1, 1, 1, 38, 129, 41, 7, 1, 1, 1, 149, 1980, 1981, 157, 8, 1, 1, 1, 703, 62611, 304495, 62616, 725, 12, 1, 1, 1, 4132, 2806490, 78322915, 78322916, 2806508, 4196, 14, 1, 1, 1, 29579, 158937213, 27033154060, 147252447227, 27033154065, 158937367, 29817, 21, 1, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 2,8 COMMENTS This sequence can be derived from A133687 and A333159. In particular, if w(n) is the inverse Euler transform of column k of A133687 and s(n) is the inverse Euler transform of column k of A333159, then 2*T(2*n+1,k) = w(2*n+1) + s(2*n+1) and 2*T(2*n,k) = w(2*n) + s(2*n) - w(n) + T(n,k).  - Andrew Howroyd, Apr 03 2020 LINKS Andrew Howroyd, Table of n, a(n) for n = 2..154 B. D. McKay and E. Rogoyski, Latin squares of order ten, Electron. J. Combinatorics, 2 (1995) #N3. EXAMPLE Triangle begins:   1;   1,   1;   1,   1,    1;   1,   2,    1,    1;   1,   5,    4,    1,   1;   1,  13,   14,    4,   1, 1;   1,  38,  129,   41,   7, 1, 1;   1, 149, 1980, 1981, 157, 8, 1, 1;   ... CROSSREFS Columns k=3..7 are A006823, A006824, A006825, A014385, A014387. Row sums are in A008323. Cf. A008327, A133687, A333159. Sequence in context: A111673 A121391 A241194 * A181196 A227578 A181783 Adjacent sequences:  A008323 A008324 A008325 * A008327 A008328 A008329 KEYWORD nonn,hard,tabl AUTHOR Brendan McKay and Eric Rogoyski EXTENSIONS More terms from Eric Rogoyski, May 15 1997 Name clarified by Andrew Howroyd, Sep 05 2018 Terms a(55) and beyond from Andrew Howroyd, Apr 03 2020 STATUS approved

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Last modified April 21 19:16 EDT 2021. Contains 343156 sequences. (Running on oeis4.)