A178689 Partial sums of A122836 (number of topologies on n labeled elements in which at least one element belongs to some pair of noncomparable members of the topology).

0, 0, 0, 10, 253, 6384, 208887, 9673189, 651633791, 63901292323, 9040801794022, 1825884406581355, 521181413335003984, 208402574279716434454, 115825454535371969786250, 88852094572776191675804592

Offset: 0

Author

Jonathan Vos Post, Dec 25 2010

Keywords

• nonn

Comments

All listed (the first 16) values are nonprimes. In the underlying sequence, only A122836(5) = 6131 is prime of the listed values.

Examples

			a(4) = 0 + 0 + 0 + 10 + 243 = 253 = 11 * 23.
		

Crossrefs

Cf. A000798, A122835, A122836.

Formula

a(n) = Sum_{i=0..n} A122836(i) = Sum_{i=0..n} (A000798(i) - A122835(i)) = (Sum_{i=0..n} A000798(i)) - (Sum_{i=0..n} A122835(i)).

Extensions

a(13)-a(15) corrected by Georg Fischer, Dec 26 2022