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A335233 Numbers m such that m!*i + 1 is composite for i = 1..m. 2

%I #66 Sep 14 2020 20:02:36

%S 50,66,67,76,81,110,117,120,122,157,178,183,217,219,226,235,240,242,

%T 244,250,254,260,266,269,274,275,287,289,309,326,346,354,363,379,380,

%U 386,400,407,410,417,419,443,449,451,470,474,489,493,509,513,518,541,543

%N Numbers m such that m!*i + 1 is composite for i = 1..m.

%C If m is a term, then A321805(m) = 0.

%H Chai Wah Wu, <a href="/A335233/b335233.txt">Table of n, a(n) for n = 1..240</a>

%t Select[Range@ 200, (f = #!; NoneTrue[f*Range[#] + 1, PrimeQ]) &] (* _Robert Price_, Sep 14 2020 *)

%o (Python)

%o from sympy import isprime

%o A335233_list, f = [], 1

%o for k in range(1,100):

%o f *= k

%o g = 1

%o for i in range(1,k+1):

%o g += f

%o if isprime(g):

%o break

%o else:

%o A335233_list.append(k)

%Y Cf. A321805.

%K nonn

%O 1,1

%A _Chai Wah Wu_, Jun 09 2020

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Last modified June 5 04:27 EDT 2024. Contains 373102 sequences. (Running on oeis4.)