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%I #9 Jan 03 2022 13:54:34
%S 0,0,0,0,0,2,3,3,3,3,0,5,8,4,10,1,4,2,5,1,11,7,1,2,6,6,11,2,9,10,18,9,
%T 32,3,8,18,15,3,18,1,18,4,2,24,14,32,149,12,1,67,49,56,1,12,10,15,3,7,
%U 17,5
%N a(n) is the least j such that (prime(n)#)*3^j + 1 is prime, where prime(n)# is the n-th primorial.
%t a[n_] := Module[{p = Product[Prime[i], {i, 1, n}], j = 0}, While[!PrimeQ[p * 3^j + 1], j++]; j]; Array[a, 100] (* _Amiram Eldar_, Sep 11 2021 *)
%t Module[{j=0},While[!PrimeQ[# 3^j+1],j++];j]&/@FoldList[ Times,Prime[ Range[60]]] (* _Harvey P. Dale_, Jan 03 2022 *)
%Y Cf. A002110.
%K nonn
%O 1,6
%A _Pierre CAMI_, Sep 04 2005
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