A071771 - OEIS

%I #9 Aug 08 2024 21:09:32

%S 59,413,2018,48907,100284,869700,23094906,272703171

%N Least k > 0 such that the nextprime(k*primorial(n)) - k*primorial(n) is composite.

%e For a(2): the second primorial (A002110) is 6. It is not until k = 413, or 6*413 = 2478, that the next prime > 2478 = 2503 less 2478 which equals 25 is a composite.

%t Do[p = Product[ Prime[i], {i, 1, n}]; k = 1; While[ q = NextPrim[k*p] - k*p; q == 1 || PrimeQ[q], k++ ]; Print[k], {n, 1, 6}]

%Y Cf. A002110, A005235, A071572.

%K nonn,more

%O 1,1

%A _David W. Wilson_ and _Robert G. Wilson v_, Jun 04 2002

%E a(8) from _Sean A. Irvine_, Aug 08 2024