A123365 Values of k such that A046530(k) = (k+2)/3, where A046530(k) is the number of distinct residues of cubes mod k.

1, 7, 13, 19, 31, 37, 43, 61, 67, 73, 79, 97, 103, 109, 127, 139, 151, 157, 163, 181, 193, 199, 211, 223, 229, 241, 271, 277, 283, 307, 313, 331, 337, 349, 367, 373, 379, 397, 409, 421, 433, 439, 457, 463, 487, 499, 523, 541, 547, 571, 577, 601, 607, 613, 619

Offset

1,2

Comments

Conjecture: With the exception of the first term a(1)=1, this is exactly the sequence of primes of the form 6k+1 (A002476). This has been verified up to a(n)=2000.

Links

R. J. Mathar, Table of n, a(n) for n = 1..10000

Jon Maiga, Computer-generated formulas for A123365, Sequence Machine.

Maple

n := 1 :
a := 1 :
while n <= 10000 do
    printf("%d %d\n", n, a) ;
    a := a+1 ;
    while A046530(a) <> (a+2)/3 do
        a := a+1 ;
    end do:
    n := n+1 ;
end do: # creates b-file, R. J. Mathar, Sep 21 2017

Crossrefs

Cf. A002476, A046530, A123722, A123723, A177965.

Sequence in context: A129389 A107925 A002476 * A144921 A272409 A272406

Adjacent sequences: A123362 A123363 A123364 * A123366 A123367 A123368

Keyword

nonn

Author

John W. Layman, Oct 12 2006

Status

approved