A364010 Semiprimes k such that none of k-2, k-1, k+1, and k+2 is squarefree.

26, 362, 926, 1027, 1126, 1574, 1774, 1814, 2059, 2402, 3482, 3574, 4166, 4474, 5042, 5045, 5374, 5426, 5914, 6274, 6326, 6418, 6626, 6649, 7226, 7694, 7985, 8182, 8674, 9026, 9458, 9557, 9874, 9946, 10774, 10826, 11851, 12223, 12494, 12574, 12949, 13349, 13474, 13526, 13582

Offset

1,1

Links

Table of n, a(n) for n=1..45.

Example

24 = 2^3 * 3, 25 = 5^2, 26 = 2 * 13, 27 = 3^3, 28 = 2^2 * 7, so 26 is a term.
360 = 2^3 * 3^2 * 5, 361 = 19^2, 362 = 2 * 181, 363 = 3 * 11^2, 364 = 2^2 * 7 * 13, so 362 is a term.

Mathematica

Select[Range[14000], PrimeOmega[#] == 2 && ! AnyTrue[# + {-2, -1, 1, 2}, SquareFreeQ] &] (* Amiram Eldar, Jul 01 2023 *)

Crossrefs

Cf. A001358, A013929, A153215. Subsequence of A364025.

Sequence in context: A162718 A010978 A022590 * A004414 A125461 A022654

Adjacent sequences: A364007 A364008 A364009 * A364011 A364012 A364013

Keyword

nonn

Author

Massimo Kofler, Jul 01 2023

Status

approved