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%I #97 Oct 03 2023 21:23:38
%S 170,530,638,874,962,1826,2526,2674,2726,2782,2874,3178,3970,4490,
%T 4526,4654,5930,6026,6254,7138,7174,8074,8126,8426,8723,8958,8974,
%U 9926,10286,10526,10610,11222,11494,11674,11710,11998,12338,12626,12770,12986,13574,15238,15274,15326,15826
%N Sphenic numbers k such that none of k-2, k-1, k+1 and k+2 is squarefree.
%e 168 = 2^3 * 3 * 7, 169 = 13^2, 170 = 2 * 5 * 17, 171 = 3^2 *19, 172 = 2^2 * 43, so 170 is a term.
%e 528 = 2^4 * 3 * 11, 529 = 23^2, 530 = 2 * 5 * 53, 531 = 3^2 * 59, 532 = 2^2 * 7 * 19, so 532 is a term.
%t Select[Range[17000], FactorInteger[#][[;; , 2]] == {1, 1, 1} && ! AnyTrue[# + {-2, -1, 1, 2}, SquareFreeQ] &] (* _Amiram Eldar_, Sep 07 2023 *)
%Y Cf. A007304, A013929, A153215, A364010. Subsequence of A364905.
%K nonn
%O 1,1
%A _Massimo Kofler_, Sep 07 2023