OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..608
FORMULA
2^a(n) = A269758(n).
EXAMPLE
a(4) = 5 because 2^5 - 1 = 31 and 2^5 + 1 = 33 are squarefree numbers.
MATHEMATICA
Select[Range[120], AllTrue[2^#+{1, -1}, SquareFreeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Dec 20 2019 *)
PROG
(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
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Juri-Stepan Gerasimov, May 01 2016
STATUS
approved