A020955 a(n) = n^(2^n - n - 1).

1, 1, 2, 81, 4194304, 1490116119384765625, 226267027688376192080197927193400943822503936, 258086210989349276047917817413172383631691140276099547911280598425927853437317437263620645695945672001

Offset

0,3

Comments

Number of finite models of natural number on the free class with n members.

Links

Table of n, a(n) for n=0..7.

Yasutoshi Kohmoto, The Other Side of Mathematics [broken link?]

Yasutoshi Kohmoto, The Other Side of Mathematics [via Internet Archive Wayback-machine]

Formula

a(n) = A097547(n)/A007778(n), n > 0. - R. J. Mathar, Jan 12 2017

Example

For n=2, a(2)=2, universe class={0,1}.
1 : { }ma 0, {0}ma 1, {0,1}ma 1, {1}ma 0,
2 : { }ma 0, {0}ma 1, {0,1}ma 1, {1}ma 1.

Crossrefs

Cf. A097547.

Sequence in context: A123177 A209585 A090603 * A230398 A120826 A343588

Adjacent sequences: A020952 A020953 A020954 * A020956 A020957 A020958

Keyword

nonn

Author

Yasutoshi Kohmoto

Extensions

a(0)=1 and a(7) corrected by Vincenzo Librandi, Apr 25 2011

Status

approved