A262204 a(n) = (2*prime(n))! / prime(n)!.

12, 120, 30240, 17297280, 28158588057600, 64764752532480000, 830034394580628357120000, 4299578163927654889881600000, 212850788988365112429784203264000000, 265847614191284935213187014536606662000640000000

Offset: 1

Author

Altug Alkan, Sep 15 2015

Keywords

• nonn
• easy

Comments

Inspired by simplicity of sequence formula that is (p + p)!/p! where p is n-th prime number.

Examples

			For n=1, a(n) = (2*prime(n))! / prime(n)! = 4!/2! = 3*4 = 12.
For n=2, a(n) = (2*prime(n))! / prime(n)! = 6!/3! = 4*5*6 = 120.
For n=3, a(n) = (2*prime(n))! / prime(n)! = 10!/5! = 6*7*8*9*10 = 30240.
		

Crossrefs

Cf. A001813, A039716, A100484, A075069, A262206.

Programs

Magma

[Factorial(NthPrime(n)+NthPrime(n)) / Factorial(NthPrime(n)): n in [1..10]]; // Vincenzo Librandi, Sep 16 2015

PARI

a(n) = (2*prime(n))!/prime(n)!;
vector(10, n, a(n))

Formula

a(n) = 2 * A075069(n).

a(n) = A001813(prime(n)). - Michel Marcus, Sep 20 2015

a(n) mod A039716(n) = 0.