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 A083663 Least k such that k*n!-1 is prime. 5

%I #11 Nov 23 2023 10:36:47

%S 3,2,1,1,2,1,1,5,3,4,4,1,5,1,2,9,2,30,30,5,44,2,7,13,5,3,11,2,14,1,7,

%T 1,1,30,16,22,36,1,38,13,22,6,36,17,36,40,31,25,38,13,4,32,22,154,10,

%U 27,7,121,9,33,19,19,4,26,100,18,46,75,21,11,34,75,38,7,45,3,19,13,59,39,72

%N Least k such that k*n!-1 is prime.

%H Robert Israel, <a href="/A083663/b083663.txt">Table of n, a(n) for n = 1..600</a>

%F a(n) = A053989(n!) = (A084730(n)+1)/n!. - _Robert Israel_, Nov 23 2023

%p f:= proc(n) local w,k;

%p w:= n!;

%p for k from 1 do

%p if isprime(k*w-1) then return k fi

%p od

%p end proc:

%p map(f, [\$1..100]); # _Robert Israel_, Nov 23 2023

%o (PARI) a(n)=if(n<1,0,k=1; while(isprime(k*n!-1)==0,k++); k)

%Y Cf. A035093, A053989, A084730.

%K nonn,changed

%O 1,1

%A _Benoit Cloitre_, Jun 14 2003

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Last modified November 30 05:42 EST 2023. Contains 367454 sequences. (Running on oeis4.)