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 A001375 Relational systems on n nodes. (Formerly M4589 N1958) 0
 8, 2080, 22386176, 11728394650624, 314824619911446167552, 450720219711043642520721817600, 35398008262453198128587489274987385192448, 155682086692129060007763454017522652304844346252853248 (list; graph; refs; listen; history; text; internal format)
 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 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: A092414 A139298 A004819 * A281651 A189308 A017415 Adjacent sequences:  A001372 A001373 A001374 * A001376 A001377 A001378 KEYWORD nonn AUTHOR EXTENSIONS More terms from Sean A. Irvine, Nov 20 2016 STATUS approved

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