Number of clouds with n points; number of undirected 2-regular labeled graphs; or number of n X n symmetric matrices with (0,1) entries, trace 0 and all row sums 2.
A001205
Number of clouds with n points; number of undirected 2-regular labeled graphs; or number of n X n symmetric matrices with (0,1) entries, trace 0 and all row sums 2.
Terms
- a(0) =1a(1) =0a(2) =0a(3) =1a(4) =3a(5) =12a(6) =70a(7) =465a(8) =3507a(9) =30016a(10) =286884a(11) =3026655a(12) =34944085a(13) =438263364a(14) =5933502822a(15) =86248951243
External references
- oeis: A001205