A001376 Relational systems on n nodes. (Formerly M3726 N1523)

4, 32896, 3002399885885440, 14178431955039103827204744901417762816, 15077094952775546279110805340148653909930339849938544191736262642546769920, 15403720522893415886546745467461576130202428237004582894538688334760691986727408991549968230000116580053960252500580634898464768

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

Table of n, a(n) for n=1..6.

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

Crossrefs

Sequence in context: A034014 A217600 A275684 * A053937 A259160 A173138

Adjacent sequences: A001373 A001374 A001375 * A001377 A001378 A001379

Keyword

nonn

Author

N. J. A. Sloane

Extensions

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

Status

approved