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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 (list; graph; refs; listen; history; text; internal format)
 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 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 A347556 A338172 Adjacent sequences:  A181833 A181834 A181835 * A181837 A181838 A181839 KEYWORD nonn AUTHOR Peter Luschny, Nov 17 2010 STATUS approved

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Last modified May 18 10:09 EDT 2022. Contains 353807 sequences. (Running on oeis4.)