A391156 Number of nonisomorphic magmas with n elements and empty center.

1, 0, 6, 2463, 168710720, 2463965471530395, 14314557500958748403432016, 50973867767312671230749731985210113185, 155681492819036209829588907196662256860643565098656504, 541851326514979120075051899545901289539707883395779770003009352752454758

Offset

0,3

Links

Andrew Howroyd, Table of n, a(n) for n = 0..25

Wikipedia, Center (algebra).

Prog

(PARI) \\ Needs permcount, C, D, E functions from A391155.
a(n) = {sum(k=0, n, my(s=0); forpart(p=k, forpart(q=n-k, my(r=concat(p, q)); s+= (-1)^#p * permcount(p) * permcount(q) * D(q, r, r) * E(p, r) )); s/(k!*(n-k)!))}

Crossrefs

Column k=0 of A391155 and A391161.

Cf. A001329, A391094 (labeled version).

Sequence in context: A279533 A069643 A264801 * A067630 A181700 A199147

Adjacent sequences: A391153 A391154 A391155 * A391157 A391158 A391159

Keyword

nonn

Author

Andrew Howroyd, Dec 10 2025

Status

approved