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A262978 Exponents n such that 2^n-1 and 2^n+1 are squarefree. 0
1, 2, 4, 5, 7, 8, 11, 13, 14, 16, 17, 19, 22, 23, 25, 26, 28, 29, 31, 32, 34, 35, 37, 38, 41, 43, 44, 46, 47, 49, 52, 53, 56, 58, 59, 61, 62, 64, 65, 67, 71, 73, 74, 76, 77, 79, 82, 83, 85, 86, 88, 89, 91, 92, 94, 95, 97, 98, 101, 103, 104, 106, 107, 109, 112, 113, 115, 116, 118, 119 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

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

EXAMPLE

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

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

Cf. A000961, A229303, A269758.

Sequence in context: A290334 A206285 A229303 * A112886 A282429 A111040

Adjacent sequences:  A262975 A262976 A262977 * A262979 A262980 A262981

KEYWORD

nonn,easy

AUTHOR

Juri-Stepan Gerasimov, May 01 2016

STATUS

approved

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Last modified September 20 08:13 EDT 2019. Contains 327214 sequences. (Running on oeis4.)