login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A058116 Triangle read by rows: T(n,k) is the number of isomorphism classes of commutative semigroups of order n with k idempotents. 6
1, 2, 1, 5, 5, 2, 16, 23, 14, 5, 62, 106, 93, 49, 15, 342, 544, 582, 422, 200, 53, 3435, 3380, 3773, 3360, 2178, 943, 222, 97061, 30788, 27222, 26625, 21283, 12676, 5072, 1078 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..36.

Index entries for sequences related to semigroups

EXAMPLE

Triangle begins:

   1;

   2,   1;

   5,   5,  2;

  16,  23, 14,  5;

  62, 106, 93, 49, 15;

  ...

CROSSREFS

Row sums give A001426.

Main diagonal is A006966(n+1).

Column 1 is A058117.

The labeled version is A058167.

Cf. A058108, A058142.

Sequence in context: A248905 A118244 A108410 * A058118 A332632 A124226

Adjacent sequences:  A058113 A058114 A058115 * A058117 A058118 A058119

KEYWORD

nonn,tabl,hard,more

AUTHOR

Christian G. Bower, Nov 09 2000

EXTENSIONS

a(29)-a(36) from Andrew Howroyd, Jan 27 2022

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 16 22:14 EDT 2022. Contains 356169 sequences. (Running on oeis4.)