A262204 a(n) = (2*prime(n))! / prime(n)!.
12, 120, 30240, 17297280, 28158588057600, 64764752532480000, 830034394580628357120000, 4299578163927654889881600000, 212850788988365112429784203264000000, 265847614191284935213187014536606662000640000000
Offset: 1
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.
Programs
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Magma
[Factorial(NthPrime(n)+NthPrime(n)) / Factorial(NthPrime(n)): n in [1..10]]; // Vincenzo Librandi, Sep 16 2015
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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.
Comments