%I M4589 N1958 #18 Nov 21 2016 10:53:50
%S 8,2080,22386176,11728394650624,314824619911446167552,
%T 450720219711043642520721817600,
%U 35398008262453198128587489274987385192448,155682086692129060007763454017522652304844346252853248
%N Relational systems on n nodes.
%D W. Oberschelp, "Strukturzahlen in endlichen Relationssystemen," in Contributions to Mathematical Logic (Proceedings 1966 Hanover Colloquium), pp. 199-213, North-Holland Publ., Amsterdam, 1968.
%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H 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]
%F 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, ...] = 8^Sum_{i, j>=1} (gcd(i,j)*s_i*s_j). - _Sean A. Irvine_, Nov 20 2016
%K nonn
%O 1,1
%A _N. J. A. Sloane_
%E More terms from _Sean A. Irvine_, Nov 20 2016