A038018 Triangle: T(n,k), k<=n: groupoids with n elements and k idempotents.

1, 0, 1, 3, 4, 3, 978, 1485, 729, 138, 56630832, 75503872, 37755904, 8390656, 700688, 813802235250650, 1017252851596875

Offset

0,4

Links

Table of n, a(n) for n=0..16.

Index entries for sequences related to groupoids

Example

Triangle begins:
         1;
         0,        1;
         3,        4,        3;
       978,     1485,      729,     138;
  56630832, 75503872, 37755904, 8390656, 700688;
  ...

Crossrefs

Row sums are A001329.

Main diagonal is A030247.

Columns k=0..1 are A030250, A030253.

Sequence in context: A288404 A287986 A190959 * A108658 A240669 A213201

Adjacent sequences: A038015 A038016 A038017 * A038019 A038020 A038021

Keyword

nonn,tabl,more

Author

Christian G. Bower, May 15 1998

Status

approved