A090602 - OEIS

%I #15 Jan 23 2022 18:26:46

%S 0,1,4,243,1048576,762939453125,170581728179578208256,

%T 18562115921017574302453163671207,

%U 1427247692705959881058285969449495136382746624,106111661199647248543687855752712667991103904330482569981872649

%N Number of n-element labeled groupoids with an identity.

%C Also labeled groupoids with an absorbant (zero) element.

%H Andrew Howroyd, <a href="/A090602/b090602.txt">Table of n, a(n) for n = 0..20</a>

%H Eric Postpischil <a href="http://groups.google.com/groups?&amp;hl=en&amp;lr=&amp;ie=UTF-8&amp;selm=11802%40shlump.nac.dec.com&amp;rnum=2">Posting to sci.math newsgroup, May 21 1990</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Groupoid.html">Groupoid</a>

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Magma_(algebra)">Magma (algebra)</a>

%H <a href="/index/Gre#groupoids">Index entries for sequences related to groupoids</a>

%F a(n) = n^((n-1)^2+1).

%F a(n) = A090603(n)*n.

%o (PARI) a(n) = n^((n-1)^2+1) \\ _Andrew Howroyd_, Jan 23 2022

%Y Cf. A090601 (isomorphism classes), A090603.

%K nonn

%O 0,3

%A _Christian G. Bower_, Dec 05 2003

%E a(0)=0 prepended and a(9) added by _Andrew Howroyd_, Jan 23 2022