A125035 - OEIS

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A125035

Numbers k such that gcd(2^k-69,k) > 1.

10, 26, 30, 50, 67, 70, 88, 90, 110, 130, 136, 150, 170, 182, 183, 185, 190, 198, 210, 212, 230, 250, 270, 272, 285, 290, 308, 310, 330, 338, 350, 370, 390, 408, 410, 413, 418, 430, 450, 470, 490, 494, 510, 528, 530, 544, 550, 570, 590, 610, 627, 630, 638, 650

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OFFSET

1,1

COMMENTS

The corresponding gcd's are 5,13,5,5,67,5,11,5,5,5,17,5,5,13,61,37,5,11, ...

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

EXAMPLE

10 is a term since gcd(2^10-69,10) = gcd(1024-69,10) = gcd(955,10) = 5 > 1.

Note that 67|(2^67-69).

MATHEMATICA

Select[Range[650], ! CoprimeQ[2^# - 69, #] &] (* Amiram Eldar, Feb 18 2022 *)