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A367791
Lesser of 2 successive tetraprimes (k, k+4) sandwiching three consecutive not squarefree numbers.
0
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
1,1
COMMENTS
Tetraprimes are the product of four distinct prime numbers (cf. A046386).
EXAMPLE
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.
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 *)
CROSSREFS
Sequence in context: A284079 A108179 A336584 * A364141 A364766 A080953
KEYWORD
nonn
AUTHOR
Massimo Kofler, Nov 30 2023
STATUS
approved