OFFSET
1,2
COMMENTS
Number of labeled trees on p(n) nodes, where p(n) is the n-th prime.
Let p = prime(n). For n >= 2, (-1)^((p-1)/2) * a(n) is the discriminant of the p-th cyclotomic polynomial. - Jianing Song, May 10 2021
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..77
FORMULA
For n >= 2, (-1)^((p-1)/2) * a(n) = A004124(p), where p = prime(n). - Jianing Song, May 10 2021
MATHEMATICA
Table[Prime@n^(Prime@n - 2), {n, 20}] (* Vincenzo Librandi, Mar 27 2014 *)
#^(#-2)&/@Prime[Range[10]] (* Harvey P. Dale, Oct 18 2016 *)
PROG
(Magma) [n^(n-2) : n in [2..40] | IsPrime(n)];
(Magma) [p^(p-2): p in PrimesUpTo(50)]; // Vincenzo Librandi, Mar 27 2014
(PARI) a(n) = my(p=prime(n)); p^(p-2) \\ Felix Fröhlich, May 10 2021
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jonathan Vos Post, Jun 18 2007
EXTENSIONS
Name edited by Felix Fröhlich, May 10 2021
STATUS
approved