A193317 Binomial(n,2)*B(n-1)*(B(n)-B(n-1)), where B() = A000110() are the Bell numbers.

0, 0, 1, 18, 300, 5550, 117780, 2873262, 80126228, 2534723280, 90239747220, 3588582531875, 158318375911740, 7700793136255440, 410691133882551795, 23894146232727414630, 1509723335738373490800, 103169903975944947302744, 7597003720932150826636260, 600748548233457344454385722

Offset

0,4

Comments

Sum of the Rand distance over all unordered pairs of partitions.

Links

Table of n, a(n) for n=0..19.

Frank Ruskey and Jennifer Woodcock, The Rand and block distances of pairs of set partitions, Combinatorial algorithms, 287-299, Lecture Notes in Comput. Sci., 7056, Springer, Heidelberg, 2011.

Mathematica

Table[Binomial[n, 2]*BellB[n - 1] (BellB[n] - BellB[n - 1]), {n, 19}] (* Michael De Vlieger, Apr 16 2015 *)

Crossrefs

Cf. A000110, A191200.

Equals half A124104.

Sequence in context: A228604 A228606 A228605 * A161599 A273434 A083451

Adjacent sequences: A193314 A193315 A193316 * A193318 A193319 A193320

Keyword

nonn

Author

N. J. A. Sloane, Aug 26 2011

Status

approved