A001375 Relational systems on n nodes. (Formerly M4589 N1958)

8, 2080, 22386176, 11728394650624, 314824619911446167552, 450720219711043642520721817600, 35398008262453198128587489274987385192448, 155682086692129060007763454017522652304844346252853248

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..8.

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, ...] = 8^Sum_{i, j>=1} (gcd(i,j)*s_i*s_j). - Sean A. Irvine, Nov 20 2016

Crossrefs

Sequence in context: A300107 A139298 A004819 * A281651 A189308 A300597

Adjacent sequences: A001372 A001373 A001374 * A001376 A001377 A001378

Keyword

nonn

Author

N. J. A. Sloane

Extensions

More terms from Sean A. Irvine, Nov 20 2016

Status

approved