A177013 a(n) is the smallest number m such that all the n numbers 1!*m-1, 2!*m-1, ..., n!*m-1 are prime.
3, 3, 3, 3, 3, 1500, 1500, 154770, 1656252, 3240034842
Offset: 1
Examples
a(5)=3 because all five numbers 1!*3-1, 2!*3-1, 3!*3-1, 4!*3-1 and 5!*3-1 are prime and 3 is the smallest such number. The corresponding primes are: n=1: 2; n=2: 2, 5; n=3: 2, 5, 17; n=4: 2, 5, 17, 71; n=5: 2, 5, 17, 71, 359; n=6: 1499, 2999, 8999, 35999, 179999, 1079999; n=7: 1499, 2999, 8999, 35999, 179999, 1079999, 7559999; n=8: 154769, 309539, 928619, 3714479, 18572399, 111434399, 780040799, 6240326399; ...
Crossrefs
Cf. A177014.
Programs
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PARI
okm(m, n) = {for (k=1, n, if (! isprime(k!*m-1), return (0));); return (1);} a(n) = {m = 1; while(! okm(m, n), m++); m;} \\ Michel Marcus, Jun 08 2014