1,2

Table of n, a(n) for n=1..70.

2^a(n) = A269758(n).

a(4) = 5 because 2^5 - 1 = 31 and 2^5 + 1 = 33 are squarefree numbers.

(MAGMA) [n: n in [1..120] | IsSquarefree(2^n-1) and IsSquarefree(2^n+1)];

(PARI) is(n)=issquarefree(2^n-1) && issquarefree(2^n+1) \\ Charles R Greathouse IV, May 02 2016

Cf. A000961, A229303, A269758.

Sequence in context: A290334 A206285 A229303 * A112886 A282429 A111040

Adjacent sequences: A262975 A262976 A262977 * A262979 A262980 A262981

nonn,easy

Juri-Stepan Gerasimov, May 01 2016

approved