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A181836
The product of primes <= n that are strongly prime to n.
10
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.
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
KEYWORD
nonn
AUTHOR
Peter Luschny, Nov 17 2010
STATUS
approved