A070251 - OEIS

A070251

Unrelated-factorial numbers: product of numbers unrelated to n (numbers which have a common divisor with n but do not divide n).

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

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OFFSET

1,6

COMMENTS

a(p) = 1 if p is a prime. 4 is the only composite number such that a(4) = 1.

LINKS

Table of n, a(n) for n=1..33.

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

Adjacent sequences: A070248 A070249 A070250 * A070252 A070253 A070254

KEYWORD

nonn

AUTHOR

Amarnath Murthy, May 05 2002

EXTENSIONS

More terms from Vladeta Jovovic, May 06 2002

STATUS

approved