|
|
A038791
|
|
An intermediate sequence for nonisomorphic circulant p^2-tournaments, indexed by odd primes p.
|
|
4
|
|
|
2, 4, 12, 104, 344, 4096, 14572, 190652, 9586984, 35791472, 1908874584, 27487790720, 104715393912, 1529755308212, 86607685141744, 4969489243995032, 19215358410149344, 1117984489315857512, 16865594581677305360, 65588423373189982912
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
2,1
|
|
COMMENTS
|
Number of subsets of {1, ..., p} with product = 1 mod p, where p is the n-th prime. - Charles R Greathouse IV, Jun 06 2013
|
|
LINKS
|
|
|
FORMULA
|
|
|
MATHEMATICA
|
has[p_] := Module[{v, u}, v = Table[0, {p-1}]; v[[1]] = 1; For[n = 2, n <= p-1, n++, u = Table[0, {p-1}]; For[j = 1, j <= p-1, j++, u[[Mod[j*n, p]]] += v[[j]]]; v += u]; 2*v[[1]]];
a[n_] := has[Prime[n]];
|
|
PROG
|
(PARI) has(p)=my(v=vector(p-1), u); v[1]=1; for(n=2, p-1, u=vector(p-1); for(j=1, p-1, u[j*n%p]+=v[j]); v+=u); 2*v[1]
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|