A001376 Relational systems on n nodes.

4, 32896, 3002399885885440, 14178431955039103827204744901417762816, 15077094952775546279110805340148653909930339849938544191736262642546769920, 15403720522893415886546745467461576130202428237004582894538688334760691986727408991549968230000116580053960252500580634898464768

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

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

• 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, ...] = 4^Sum_{i, j, k>=1} (i*j*k*s_i*s_j*s_k/lcm(i, j, k)). - Sean A. Irvine, Nov 20 2016

Extensions

a(5)-a(6) from Sean A. Irvine, Nov 20 2016