A140186 Number of connected groupoids (categories all of whose morphisms are invertible) with n more morphisms than objects.

2, 1, 2, 2, 1, 2, 3, 5, 2, 2, 2, 5, 2, 2, 3, 15, 1, 5, 2, 5, 3, 2, 3, 15, 3, 2, 6, 4, 2, 4, 7, 51, 1, 4, 3, 14, 1, 2, 4, 14, 1, 6, 4, 4, 3, 3, 6, 52, 2, 5, 2, 7, 1, 15, 4, 13, 3, 2, 2, 13, 4, 2, 18, 267, 1, 4, 3, 5, 1, 9, 7, 50, 2, 2, 4, 4, 2, 6, 8, 52, 15, 2, 3, 15, 1, 2, 3, 14, 1, 10, 3, 5, 4

Offset

0,1

Comments

a(n) >= A000001(n+1) (number of groups of order n+1).

Links

Table of n, a(n) for n=0..92.

Formula

a(0) = 2 and if n>0, a(n) = sum(A000001((n+k)/(k^2)),k^2|n+k). (see formula for A140185)

Crossrefs

Cf. A140185, A140187, A140188.

Sequence in context: A271106 A273673 A376570 * A078498 A350700 A178522

Adjacent sequences: A140183 A140184 A140185 * A140187 A140188 A140189

Keyword

nonn

Author

Benoit Jubin, May 12 2008

Status

approved