A306257 a(n) = t for the minimal integer k > t such that k^2 mod n = t^2 is a perfect square.

0, 0, 1, 0, 2, 2, 2, 1, 0, 3, 3, 2, 3, 3, 1, 0, 4, 0, 4, 4, 2, 4, 4, 1, 0, 5, 3, 5, 5, 2, 5, 2, 4, 5, 1, 0, 6, 6, 5, 3, 6, 4, 6, 6, 2, 6, 6, 1, 0, 0, 7, 7, 7, 6, 3, 5, 5, 7, 7, 2, 7, 7, 1, 0, 4, 8, 8, 8, 7, 2, 8, 3, 8, 8, 5, 8, 2, 7, 8, 1, 0, 9, 9, 4, 6, 9, 7, 9, 9, 4, 3, 9, 8, 9, 7, 2, 9, 0, 1, 0, 10, 8, 10, 9, 4

Offset: 1

Author

Alois P. Heinz, Feb 13 2019

Keywords

• nonn
• look

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..20000

Crossrefs

Cf. A000290, A077591, A306271 (values of k).

Programs

Maple

a:= proc(n) local k; for k from (s-> `if`(s^2
				

Formula

a(n) = 0 <=> n > 0 and n in { A000290 } union { A077591 }.