1,1

Subsequence of A013929 and A067874.

Table of n, a(n) for n=1..62.

4 is in this sequence because 4 = 2^2 is nonsquarefree and both 4 - 1 = 3 and 4 + 1 = 5 are squarefree.

(MAGMA) [n: n in [2..300] | not IsSquarefree(n) and IsSquarefree(n-1) and IsSquarefree(n+1)];

(PARI) isok(n) = !issquarefree(n) && issquarefree(n-1) && issquarefree(n+1); \\ Michel Marcus, Jun 18 2017

Cf. A013929, A067874, A228649, A272799, A281192.

Sequence in context: A137257 A144976 A119622 * A328840 A255411 A067575

Adjacent sequences: A280889 A280890 A280891 * A280893 A280894 A280895

nonn,easy

Juri-Stepan Gerasimov, Jan 16 2017

Definition corrected by Jon E. Schoenfield, Jun 18 2017

approved