A239580 Numbers k such that A227364(k) = 1 + 2*3 + 4*5*6 + 7*8*9*10 + ... + ...*k is a prime.

2, 3, 4, 6, 9, 10, 13, 14, 15, 18, 30, 32, 54, 58, 59, 81, 85, 128, 140, 203, 204, 206, 209, 223, 286, 305, 343, 350, 367, 397, 399, 451, 453, 506, 534, 656, 676, 698, 730, 756, 845, 849, 878, 944, 1020, 1040, 1091, 1248, 1256, 1300, 1310, 1326, 1364, 1406, 1535

Offset: 1

Author

Alex Ratushnyak, Mar 21 2014

Keywords

• nonn

Crossrefs

Cf. A227364.

Programs

Python

from sympy import isprime
for n in range(10000):
  sum_ = 0
  i = k = 1
  while i<=n:
    product = 1
    for x in range(k):
      product *= i
      i += 1
      if i>n: break
    sum_ += product
    k += 1
  if isprime(sum_):  print(n, end=', ')