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A000662 Relations with 3 arguments on n nodes.
(Formerly M2180 N0872)
7
2, 136, 22377984, 768614354122719232, 354460798875983863749270670915141632, 146267071761884981524915186989628577728537526896649216991428608 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

F. Bergeron, G. Labelle and P. Leroux, Combinatorial Species and Tree-Like Structures, Cambridge, 1998, p. 76 (2.2.31)

W. Oberschelp, Kombinatorische Anzahlbestimmungen in Relationen, Math. Ann., 174 (1967), 53-78.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..15

P. J. Cameron, Sequences realized by oligomorphic permutation groups, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.

W. Oberschelp, Strukturzahlen in endlichen Relationssystemen, in Contributions to Mathematical Logic (Proceedings 1966 Hanover Colloquium), pp. 199-213, North-Holland Publ., Amsterdam, 1968. [Annotated scanned copy]

FORMULA

a(n) = sum_{1*s_1+2*s_2+...=n} (fix A[s_1, s_2,...]/(1^s_1*s_1!*2^s_2*s_2!*...)) where fix A[s_1, s_2, ...] = 2^sum_{i, j, k>=1} (i*j*k*s_i*s_j*s_k/lcm(i, j, k)).

CROSSREFS

Cf. A000595, A001377, A051241.

Sequence in context: A226118 A216030 A216083 * A139907 A195379 A221227

Adjacent sequences:  A000659 A000660 A000661 * A000663 A000664 A000665

KEYWORD

nonn,nice

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Formula from Christian G. Bower, Jan 06 2004

STATUS

approved

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Last modified February 21 19:50 EST 2018. Contains 299423 sequences. (Running on oeis4.)