A038020 - OEIS

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A038020

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

1

0, 0, 0, 2, 0, 2, 9, 54, 0, 30, 15376, 12664, 14304, 4096, 3187

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OFFSET

0,4

LINKS

Table of n, a(n) for n=0..14.

Index entries for sequences related to groupoids

FORMULA

Difference of A038018 and A038019.

EXAMPLE

Triangle begins:

0;

0, 0;

2, 0, 2;

9, 54, 0, 30;

15376, 12664, 14304, 4096, 3187;

...

CROSSREFS

Row sums are A030246.

Main diagonal is A030249.

Columns k=0..1 are A030252, A030254.

Cf. A001329, A030248, A030251, A030271.

Sequence in context: A091518 A096734 A220234 * A211910 A250406 A107094

Adjacent sequences: A038017 A038018 A038019 * A038021 A038022 A038023

KEYWORD

nonn,tabl,more

AUTHOR

Christian G. Bower, May 15 1998

STATUS

approved