A364141 Products k of 4 distinct primes (or tetraprimes) such that k has no squarefree neighbors.

3774, 5565, 6726, 8151, 10659, 10934, 11726, 11935, 12426, 13035, 13195, 13674, 13755, 14763, 15042, 15249, 15351, 15785, 16215, 16226, 17630, 17765, 17974, 17985, 18249, 18278, 18915, 18998, 19565, 20085, 21385, 21574, 21855, 22015, 23023, 23345, 23374, 23426, 24038, 24605, 25185

Offset

1,1

Links

Table of n, a(n) for n=1..41.

Example

3773 = 7^3 * 11, 3774 = 2 * 3 * 17 * 37, 3775 = 5^2 * 151, so 3774 is a term.
5564 = 2^2 * 13 * 107, 5565 = 3 * 5 * 7 * 53, 5566 = 2 * 11^2 * 23, so 5565 is a term.

Mathematica

Select[Range[26000], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1} && ! SquareFreeQ[# - 1] && ! SquareFreeQ[# + 1] &] (* Amiram Eldar, Jul 10 2023 *)

Crossrefs

Cf. A013929, A046386.

Sequence in context: A108179 A336584 A367791 * A364766 A080953 A178193

Adjacent sequences: A364138 A364139 A364140 * A364142 A364143 A364144

Keyword

nonn

Author

Massimo Kofler, Jul 10 2023

Status

approved