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Prime numbers n such that n-1 is squarefree and all prime divisors of n-1 other than 19 are in the sequence.
5

%I #29 Nov 24 2021 11:35:07

%S 2,3,7,43,4903,168241543,5773040306503

%N Prime numbers n such that n-1 is squarefree and all prime divisors of n-1 other than 19 are in the sequence.

%t S[1] = {2, 19}; PR[S_] := Product[S[[i]], {i, Length[S]}];

%t S[m_] := S[m] = Union[S[m - 1], Select[Table[PR[Subsets[S[m - 1]] [[i]]] + 1, {i, 2^Length[S[m - 1]]}], PrimeQ]]; A267507 = Complement[S[7], {19}]

%t (* S[7]=S[8] ==> sequence is finite and full; _José María Grau Ribas_, Nov 22 2021 *)

%Y Cf. A267503, A267504, A267505, A267506, A267507.

%K nonn,fini,full

%O 1,1

%A _José María Grau Ribas_, Jan 16 2016