cp's OEIS Frontend

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

%I A239580 #12 Aug 08 2025 11:28:56
%S A239580 2,3,4,6,9,10,13,14,15,18,30,32,54,58,59,81,85,128,140,203,204,206,
%T A239580 209,223,286,305,343,350,367,397,399,451,453,506,534,656,676,698,730,
%U A239580 756,845,849,878,944,1020,1040,1091,1248,1256,1300,1310,1326,1364,1406,1535
%N A239580 Numbers k such that A227364(k) = 1 + 2*3 + 4*5*6 + 7*8*9*10 + ... + ...*k  is a prime.
%o A239580 (Python)
%o A239580 from sympy import isprime
%o A239580 for n in range(10000):
%o A239580   sum_ = 0
%o A239580   i = k = 1
%o A239580   while i<=n:
%o A239580     product = 1
%o A239580     for x in range(k):
%o A239580       product *= i
%o A239580       i += 1
%o A239580       if i>n: break
%o A239580     sum_ += product
%o A239580     k += 1
%o A239580   if isprime(sum_):  print(n, end=', ')
%Y A239580 Cf. A227364.
%K A239580 nonn
%O A239580 1,1
%A A239580 _Alex Ratushnyak_, Mar 21 2014