A127920 1/6 of product of three numbers: n-th prime, previous and following number.

1, 4, 20, 56, 220, 364, 816, 1140, 2024, 4060, 4960, 8436, 11480, 13244, 17296, 24804, 34220, 37820, 50116, 59640, 64824, 82160, 95284, 117480, 152096, 171700, 182104, 204156, 215820, 240464, 341376, 374660, 428536, 447580, 551300, 573800, 644956

Offset: 1

Author

Artur Jasinski, Feb 06 2007

Keywords

• nonn
• easy

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A036689, A034953, A127917, A127918, A127919.

Programs

Magma

[(NthPrime(n) + 1)*NthPrime(n)*(NthPrime(n) - 1)/6: n in [1..40]]; // Vincenzo Librandi, Apr 09 2017

Mathematica

Table[(Prime[n] + 1) Prime[n](Prime[n] - 1)/6, {n, 1, 100}]
((#-1)#(#+1))/6&/@Prime[Range[40]] (* Harvey P. Dale, Dec 23 2019 *)

PARI

forprime(p=2,1e3,print1(binomial(p+1,3)", ")) \\ Charles R Greathouse IV, Jun 16 2011

Python

from sympy import prime
print([(prime(n) - 1)*prime(n)*(prime(n) + 1)//6 for n in range(1, 101)]) # Indranil Ghosh, Apr 09 2017

Formula

a(n) = A127918(n)/3. - Michel Marcus, Apr 09 2017