login
A070251
Unrelated-factorial numbers: product of numbers unrelated to n (numbers which have a common divisor with n but do not divide n).
2
1, 1, 1, 1, 1, 4, 1, 6, 6, 192, 1, 720, 1, 23040, 6480, 10080, 1, 12902400, 1, 34836480, 2449440, 1857945600, 1, 50295168000, 3000, 980995276800, 9797760, 9564703948800, 1, 1518492398911488000, 1, 41845579776000, 1571364748800
OFFSET
1,6
COMMENTS
a(p) = 1 if p is a prime. 4 is the only composite number such that a(4) = 1.
FORMULA
a(n) = A055067(n)/A001783(n). - Vladeta Jovovic, May 06 2002
MAPLE
A070251 := proc(n) local i;
remove(k->igcd(n, k)=1, {$1..n}); numtheory[divisors](n);
mul(i, i = %% minus % ) end: # Peter Luschny, Oct 11 2011
MATHEMATICA
a[n_] := Times @@ Complement[Range[n], Divisors[n]]/Times @@ Select[ Range[n], CoprimeQ[n, #]&];
Array[a, 33] (* Jean-François Alcover, Jun 03 2019 *)
CROSSREFS
Sequence in context: A193529 A214561 A066575 * A373918 A134234 A207628
KEYWORD
nonn
AUTHOR
Amarnath Murthy, May 05 2002
EXTENSIONS
More terms from Vladeta Jovovic, May 06 2002
STATUS
approved