This is to A000679 as semigroups are to groups.
Table of n, a(n) for n=0..3.
a(n) = A027851(A000079(n)).
a(3) = 3684030417 because there are 3684030417 nonisomorphic semigroups of order 2^3 = 8.
Cf. A000079, A000679 Number of groups of order 2^n, A027851 Number of nonisomorphic semigroups of order n.
Sequence in context: A208410 A268001 A096543 * A138733 A222363 A316330
Adjacent sequences: A209409 A209410 A209411 * A209413 A209414 A209415
Jonathan Vos Post, Mar 08 2012