A001377 Number of relations with 4 arguments on n nodes. (Formerly M2189 N0875)

2, 32896, 402975273205975947935744, 4824670384888174809315457708695329515706856139873561594988392833332671414272

Offset

1,1

References

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

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..7

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]

Prog

(Python)
from itertools import product
from math import factorial, prod, lcm
from fractions import Fraction
from sympy.utilities.iterables import partitions
def A001377(n): return int(sum(Fraction(1<<sum(prod(r)//lcm(*r)*prod(p[d] for d in r) for r in product(p.keys(), repeat=4)), prod(q**p[q]*factorial(p[q]) for q in p)) for p in partitions(n))) # Chai Wah Wu, Jul 02 2024

Crossrefs

Cf. A000595, A000662, A051241.

Sequence in context: A176721 A030462 A228556 * A206854 A330304 A272166

Adjacent sequences: A001374 A001375 A001376 * A001378 A001379 A001380

Keyword

nonn,nice

Author

N. J. A. Sloane

Extensions

More terms from Vladeta Jovovic

Status

approved