A355846 a(n) = A066653(n+1)/3.

1, 2, 5, 7, 10, 17, 23, 38, 47, 58, 70, 77, 95, 103, 107, 110, 137, 143, 170, 182, 205, 215, 217, 238, 247, 278, 283, 287, 298, 313, 322, 347, 355, 373, 385, 397, 443, 455, 467, 542, 562, 565, 577, 590, 593, 653, 655, 667, 670, 682, 703, 707, 710, 737, 758, 773, 787, 835, 907

Offset: 1

Author

Wesley Ivan Hurt, Jul 18 2022

Keywords

• nonn

Comments

Apart from the initial 2 in A066653, same as (A066653)/3. All terms are squarefree. No term is a multiple of 3.

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A066653.

Programs

Mathematica

(Select[Prime@ Range[3, 720], And[SquareFreeQ[(# + 1)/2], PrimeQ[# + 2]] &] + 1)/6 (* Michael De Vlieger, Jul 25 2022 *)

PARI

isok(k) = issquarefree(k) && isprime(2*k-1) && isprime(2*k+1); \\ A066653
lista(nn) = my(list = List()); for (n=3, nn, if (isok(n), listput(list, n/3));); Vec(list); \\ Michel Marcus, Jul 25 2022