A282689 -id:A282689 - cp's OEIS frontend

A280149 Numbers k such that 3^k - 2^k is not squarefree.

10, 11, 20, 22, 30, 33, 40, 42, 44, 50, 52, 55, 57, 60, 66, 70, 77, 80, 84, 88, 90, 99, 100, 104, 110, 114, 120, 121, 126, 130, 132, 140, 143, 150, 154, 156, 160, 165, 168, 170, 171, 176, 180, 187, 190, 198, 200, 203, 208, 209, 210, 220, 228, 230, 231, 240, 242, 250, 252, 253, 260, 264, 270, 272, 275, 280, 285

Offset: 1

Juri-Stepan Gerasimov, Dec 27 2016

nonn

Primitive members (not multiples of earlier terms) are 10, 11, 42, 52, 57, 203, 272, 497, .... - Juri-Stepan Gerasimov and Charles R Greathouse IV, Dec 27 2016
From Robert Israel, Dec 27 2016: (Start)
Numbers divisible by the order of 3/2 mod p^2 for some prime p > 3.
Includes numbers divisible by p^2-p for some prime p > 3.
If k is a member, then so are all multiples of k. (End)

			10 is in this sequence because 3^10 - 2^10 = 58025 = 5^2*11*211.

Charles R Greathouse IV and Amiram Eldar, Table of n, a(n) for n = 1..134 (terms 1..127 from Charles R Greathouse IV)

Cf. A001047, A005117, A013929, A049094, A057468, A082869, A282688, A282689.

[n: n in [1..156] | not IsSquarefree(3^n-2^n)];

Select[Range@ 120, ! SquareFreeQ[3^# - 2^#] &] (* Michael De Vlieger, Dec 27 2016 *)

is(n)=issquarefree(3^n-2^n)==0 \\ Charles R Greathouse IV, Dec 27 2016

More terms from Charles R Greathouse IV, Dec 27 2016

A282688 Square root of the smallest square referenced in A280149 (Numbers n such that 3^n - 2^n is not squarefree).

Original entry on oeis.org

5, 23, 5, 23, 5, 23, 5, 7, 23, 5, 13, 23, 19, 5, 23, 5, 23, 5, 7, 23, 5, 23, 5, 13, 5, 19, 5, 23, 7, 5, 23, 5, 23, 5, 23, 13, 5, 23, 7, 5, 19, 23, 5, 23, 5, 23, 5, 29, 13, 23, 5, 5, 19, 5, 23, 5, 23, 5, 7, 23, 5, 23, 5, 17, 23, 5, 19, 23, 5, 7, 23, 5, 23, 5

Offset: 1

Robert Price, Feb 20 2017

nonn

			A280149(1)=10, 3^10-2^10=58025, 58025=5*5*11*211, so 58025 is not squarefree the square being 5*5=25, the square root being 5.

Robert Price, Table of n, a(n) for n = 1..127

Cf. A280149, A282689.

cp's OEIS Frontend

A280149 Numbers k such that 3^k - 2^k is not squarefree.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

Magma

Mathematica

PARI

Extensions