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%I #9 Dec 23 2023 16:42:28
%S 3770,12122,12426,17574,19158,22074,28574,31506,40922,46322,47382,
%T 50930,52854,57174,60378,61586,66174,72474,74222,77231,78774,85074,
%U 85526,87954,89090,91322,91374,95226,97622,99582,104210,106674,113734,118374,120786,122822,124674,126870,127673
%N Lesser of 2 successive tetraprimes (k, k+4) sandwiching three consecutive not squarefree numbers.
%C Tetraprimes are the product of four distinct prime numbers (cf. A046386).
%e 3770 = 2*5*13*29, 3771 = 3^2*419, 3772 = 2^2*23*41, 3773 = 7^3*11, 3774 = 2*3*17*37, so 3770 is a term.
%e 12122 = 2*11*19*29, 12123 = 3^3*449, 12124 = 2^2*7*433, 12125 = 5^3*97, 12126 = 2*3*43*47, so 12122 is a term.
%t f[n_] := Module[{e = FactorInteger[n][[;; , 2]]}, If[e == {1, 1, 1, 1}, 1, If[AnyTrue[e, # > 1 &], 2, 0]]]; Position[Partition[Array[f, 130000], 5, 1], {1, 2, 2, 2, 1}][[;; , 1]] (* _Amiram Eldar_, Nov 30 2023 *)
%Y Cf. A046386, A013929.
%K nonn
%O 1,1
%A _Massimo Kofler_, Nov 30 2023