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Numbers x = LCM(1,2,...,k) such that x^2 + 1 is prime.
1

%I #10 Aug 23 2024 08:42:00

%S 1,2,6,420,360360,718766754945489455304472257065075294400

%N Numbers x = LCM(1,2,...,k) such that x^2 + 1 is prime.

%C The next term has k > 10^4, if it exists. - _Amiram Eldar_, Aug 23 2024

%t Select[FoldList[LCM, 1, Select[Range[100], PrimePowerQ]], PrimeQ[#^2 + 1] &] (* _Amiram Eldar_, Aug 23 2024 *)

%Y Cf. A003418, A049536, A046029, A051418, A051451, A051739, A053609.

%K nonn,hard

%O 1,2

%A _Labos Elemer_, Feb 09 2000