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

0,5

Links

Table of n, a(n) for n=0..27.

Formula

a(n) is squarefree.

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);

Crossrefs

Cf. A181836, A181832, A001783.

Sequence in context: A377612 A168211 A131876 * A126070 A393533 A305998

Adjacent sequences: A325133 A325134 A325135 * A325137 A325138 A325139

Keyword

nonn

Author

Peter Luschny, Apr 01 2019

Status

approved