OFFSET
1,3
COMMENTS
Of the values shown, only 3 is prime. Are there any other prime values in the sequence? - Jonathan Vos Post, Dec 29 2011
EXAMPLE
The first symmetric, reflexive, nontransitive relation occurs for n=3: omitting a non-identical couple (a,b) from the total relation gives such a relation (and for n=3, this is the only way). There are 3 ways to choose this couple.
PROG
(Sage) def a(n): return 2^(n*(n-1)/2) - bell_number(n)
CROSSREFS
KEYWORD
nonn
AUTHOR
Bert Seghers, Dec 20 2011
STATUS
approved