A123722 Values of n for which A000224(n)=Ceiling[(n+1)/3]; A000224(n) is the number of squares mod n.

1, 3, 4, 8, 9, 15, 21, 33, 35, 39, 51, 57, 69, 70, 87, 93, 111, 123, 129, 141, 159, 177, 183, 201, 213, 219, 237, 249, 267, 291, 303, 309, 321, 327, 339, 381, 393, 411, 417, 447, 453, 471, 489, 501, 519, 537, 543, 573, 579, 591, 597, 633, 669, 681, 687, 699, 717

Offset: 1

Author

John W. Layman, Oct 09 2006

Keywords

• nonn

Comments

Conjecture. If n>2 and a(n) is a multiple of 3, then a(n)/3 is a prime; further, all odd primes are given as a(n)/3 for some n. (This has been verified up to n=2000.)

Crossrefs

Cf. A000224, A123723.