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A123722
Values of n for which A000224(n)=Ceiling[(n+1)/3]; A000224(n) is the number of squares mod n.
2
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
1,2
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
Sequence in context: A135276 A058074 A319875 * A328733 A217788 A273257
KEYWORD
nonn
AUTHOR
John W. Layman, Oct 09 2006
STATUS
approved