cp's OEIS Frontend

A001377 Number of relations with 4 arguments on n nodes.

%I A001377 M2189 N0875 #37 Jul 02 2024 15:12:10
%S A001377 2,32896,402975273205975947935744,
%T A001377 4824670384888174809315457708695329515706856139873561594988392833332671414272
%N A001377 Number of relations with 4 arguments on n nodes.
%D A001377 W. Oberschelp, "Strukturzahlen in endlichen Relationssystemen", in Contributions to Mathematical Logic (Proceedings 1966 Hanover Colloquium), pp. 199-213, North-Holland Publ., Amsterdam, 1968.
%D A001377 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A001377 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A001377 Alois P. Heinz, <a href="/A001377/b001377.txt">Table of n, a(n) for n = 1..7</a>
%H A001377 P. J. Cameron, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL3/groups.html">Sequences realized by oligomorphic permutation groups</a>, J. Integ. Seqs. Vol. 3 (2000), #00.1.5.
%H A001377 W. Oberschelp, <a href="/A000662/a000662.pdf">Strukturzahlen in endlichen Relationssystemen</a>, in Contributions to Mathematical Logic (Proceedings 1966 Hanover Colloquium), pp. 199-213, North-Holland Publ., Amsterdam, 1968. [Annotated scanned copy]
%o A001377 (Python)
%o A001377 from itertools import product
%o A001377 from math import factorial, prod, lcm
%o A001377 from fractions import Fraction
%o A001377 from sympy.utilities.iterables import partitions
%o A001377 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
%Y A001377 Cf. A000595, A000662, A051241.
%K A001377 nonn,nice
%O A001377 1,1
%A A001377 _N. J. A. Sloane_
%E A001377 More terms from _Vladeta Jovovic_