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

0,4

Comments

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

Links

Table of n, a(n) for n=0..15.

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)).

Example

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

Crossrefs

Cf. A000798, A122835, A122836.

Sequence in context: A240289 A001536 A114450 * A095983 A059166 A100743

Adjacent sequences: A178686 A178687 A178688 * A178690 A178691 A178692

Keyword

nonn

Author

Jonathan Vos Post, Dec 25 2010

Extensions

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

Status

approved