A181836 The product of primes <= n that are strongly prime to n.

1, 1, 1, 1, 1, 3, 1, 5, 15, 35, 7, 21, 35, 385, 165, 143, 1001, 15015, 5005, 85085, 51051, 46189, 20995, 440895, 1616615, 7436429, 1716099, 2860165, 5311735, 15935205, 7436429, 215656441, 3234846615

Offset

0,6

Comments

k is strongly prime to n iff k is relatively prime to n and k does not divide n-1.

Links

Table of n, a(n) for n=0..32.

Peter Luschny, Strong coprimality.

Example

a(11) = 3 * 7 = 21.

Maple

with(numtheory):
Primes := n -> select(k->isprime(k), {$1..n}):
StrongCoprimes := n -> select(k->igcd(k, n)=1, {$1..n}) minus divisors(n-1):
StrongCoprimePrimes := n -> Primes(n) intersect StrongCoprimes(n):
A181836 := proc(n) local i; mul(i, i=StrongCoprimePrimes(n)) end:

Mathematica

a[n_] := Times @@ Select[Range[2, n], PrimeQ[#] && CoprimeQ[#, n] && !Divisible[n-1, #] &]; Table[a[n], {n, 0, 32}] (* Jean-François Alcover, Jun 28 2013 *)

Crossrefs

Cf. A181831, A181832, A181833, A181834, A181835, A001783.

Sequence in context: A059616 A125053 A291665 * A124740 A369121 A347556

Adjacent sequences: A181833 A181834 A181835 * A181837 A181838 A181839

Keyword

nonn

Author

Peter Luschny, Nov 17 2010

Status

approved