A002502 Number of connected relations.

1, 65, 1795, 36317, 636331, 10365005, 162470155, 2495037197, 37898120011, 572284920845, 8614868501515, 129467758660877, 1943971108806091, 29175170378428685, 437752102106036875, 6567275797761209357

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• nice
• easy

References

• 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

• T. D. Noe, Table of n, a(n) for n=1..100
• G. Kreweras, Inversion des polynômes de Bell bidimensionnels et application au dénombrement des relations binaires connexes. C. R. Acad. Sci. Paris Ser. A-B 268 1969 A577-A579.
• Index entries for linear recurrences with constant coefficients, signature (38,-539,3622,-11640,14400).

Crossrefs

Cf. A005333, A001047, A002501, A093732, A093733.

A diagonal of A262307.

Programs

Mathematica

LinearRecurrence[{38,-539,3622,-11640,14400},{1,65,1795,36317,636331},20] (* Harvey P. Dale, Mar 24 2017 *)

Formula

15^n-4*8^n-3*6^n+12*5^n-6*4^n. - Goran Kilibarda, Vladeta Jovovic, Apr 14 2004

G.f. x*( -1-27*x+136*x^2+480*x^3 ) / ( (6*x-1)*(5*x-1)*(15*x-1)*(4*x-1)*(8*x-1) ).

- R. J. Mathar, Jun 09 2013

Extensions

More terms from Goran Kilibarda, Vladeta Jovovic, Apr 14 2004