A325136 The product of primes <= 2n that are strongly prime to 2n, bisection of A181836.

1, 1, 1, 1, 15, 7, 35, 165, 1001, 5005, 51051, 20995, 1616615, 1716099, 5311735, 7436429, 3234846615, 178752665, 955049953, 5277907635, 19027533679, 176684241305, 13829557433055, 18960523669087, 2180460221945005, 8784139751264163, 463717784757535, 102481630431415235

Offset: 0

Author

Peter Luschny, Apr 01 2019

Keywords

• nonn

Crossrefs

Cf. A181836, A181832, A001783.

Programs

Maple

primes := n -> select(k -> isprime(k), {$1..n}):
strong_prime_to := n -> select(k -> igcd(k,n) = 1, primes(n)) minus numtheory:-divisors(n-1):
A325136 := n -> mul(k, k in strong_prime_to(2*n)):
seq(A325136(n), n=0..27);

Formula

a(n) is squarefree.