cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A002787 Number of semigroups of order n with 2 idempotents, considered to be equivalent when they are isomorphic or anti-isomorphic (by reversal of the operator).

Table of values

n a(n)
2 2
3 7
4 37
5 216
6 1780
7 32652
8 4665709
9 12710266442
10 381279977009776

List of values

[2, 7, 37, 216, 1780, 32652, 4665709, 12710266442, 381279977009776]