A367791 Lesser of 2 successive tetraprimes (k, k+4) sandwiching three consecutive not squarefree numbers.

3770, 12122, 12426, 17574, 19158, 22074, 28574, 31506, 40922, 46322, 47382, 50930, 52854, 57174, 60378, 61586, 66174, 72474, 74222, 77231, 78774, 85074, 85526, 87954, 89090, 91322, 91374, 95226, 97622, 99582, 104210, 106674, 113734, 118374, 120786, 122822, 124674, 126870, 127673

Offset: 1

Author

Massimo Kofler, Nov 30 2023

Keywords

• nonn

Comments

Tetraprimes are the product of four distinct prime numbers (cf. A046386).

Examples

			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.
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.
		

Crossrefs

Cf. A046386, A013929.

Programs

Mathematica

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 *)