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A193814 Least k such that n! + k + 1 is a prime. 0

%I

%S 0,0,0,0,4,6,6,10,22,16,10,0,28,66,18,42,22,30,36,88,28,30,30,96,130,

%T 40,58,0,66,222,106,126,78,36,96,60,130,0,42,96,52,0,96,70,46,238,100,

%U 232,52,82,60,270,52,70,222,70,148,106,282,292,270,768,130,270,66

%N Least k such that n! + k + 1 is a prime.

%F a(n) = 0 for n in A002981. - _Michel Marcus_, Oct 10 2019

%e a(5) = 6 because 5! + 6 + 1 = 127 is prime.

%t a={};Do[k = 0; While[ !PrimeQ[n! + k + 1], k++ ]; AppendTo[a, k], {n, 0, 70} ];a

%t ld[n_]:=Module[{f=n!},NextPrime[f]-f-1]; Array[ld,70,0] (* _Harvey P. Dale_, Jul 13 2014 *)

%o (PARI) a(n) = my(k=0); while (!isprime(n!+k+1), k++); k; \\ _Michel Marcus_, Oct 10 2019

%Y Cf. A002981

%K nonn

%O 0,5

%A _Michel Lagneau_, Aug 06 2011

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Last modified August 16 21:38 EDT 2022. Contains 356169 sequences. (Running on oeis4.)