A356094 a(n) = denominator((prime(n)-1)/prime(n)#), where prime(n)# = A002110(n) is the n-th primorial.

2, 3, 15, 35, 231, 5005, 255255, 1616615, 10140585, 462120945, 6685349671, 1236789689135, 30425026352721, 311494317420715, 13367169186706335, 1253429172199617105, 33151040519900217915, 3909612711980232366109, 119065478046670712967865, 7970583287524270870963077

Offset: 1

Author

Amiram Eldar, Jul 26 2022

Keywords

• nonn
• frac

Comments

See A356093 for details.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..351

Crossrefs

Cf. A002110, A356093 (numerators).

Similar sequences: A038111, A338560, A340819, A341432, A342451, A342480.

Programs

Mathematica

primorial[n_] := Product[Prime[i], {i, 1, n}]; Denominator[Table[(Prime[i] - 1)/primorial[i], {i, 1, 20}]]

PARI

a(n) = denominator((prime(n)-1)/factorback(primes(n))); \\ Michel Marcus, Jul 26 2022

Python

from math import gcd
from sympy import primorial, prime
def A356094(n): return (p:=primorial(n))//gcd(p,prime(n)-1) # Chai Wah Wu, Jul 26 2022