A364766 Products k of 4 distinct primes (or tetraprimes) such that none of k-2, k-1, k+1 and k+2 is squarefree.

3774, 6726, 10934, 11726, 12426, 13674, 15042, 16226, 17630, 17974, 18278, 18998, 21574, 23374, 23426, 24038, 27710, 27874, 28826, 32390, 34390, 35074, 35126, 37630, 37774, 38170, 38626, 41210, 41426, 46342, 46774, 46990, 47874, 50518, 50806, 51794, 53074, 53846

Offset

1,1

Links

Table of n, a(n) for n=1..38.

Example

3772 = 2^2 * 23 * 41, 3773 = 7^3 * 11, 3774 = 2 * 3 * 17 * 37, 3775 = 5^2 * 151, 3776 = 2^6 * 59, so 3774 is a term.
6724 = 2^2 * 41^2, 6725 = 5^2 * 269, 6726 = 2 * 3 * 19 * 59, 6727 = 7 * 31^2, 6728 = 2^3 * 29^2, so 6726 is a term.

Mathematica

Select[Range[55000], FactorInteger[#][[;; , 2]] == {1, 1, 1, 1} && !AnyTrue[# + {-2, -1, 1, 2}, SquareFreeQ] &] (* Amiram Eldar, Aug 06 2023 *)

Crossrefs

Cf. A013929, A046386. Subsequence of A364141.

Sequence in context: A336584 A367791 A364141 * A080953 A178193 A243777

Adjacent sequences: A364763 A364764 A364765 * A364767 A364768 A364769

Keyword

nonn

Author

Massimo Kofler, Aug 06 2023

Status

approved