login
A354597
a(n) is the smallest number k>0 such that -n is not a quadratic residue modulo k.
1
3, 4, 5, 3, 4, 4, 3, 5, 4, 3, 7, 5, 3, 4, 7, 3, 4, 4, 3, 11, 4, 3, 5, 9, 3, 4, 5, 3, 4, 4, 3, 5, 4, 3, 8, 7, 3, 4, 7, 3, 4, 4, 3, 7, 4, 3, 5, 5, 3, 4, 7, 3, 4, 4, 3, 11, 4, 3, 8, 7, 3, 4, 5, 3, 4, 4, 3, 5, 4, 3, 7, 5, 3, 4, 8, 3, 4, 4, 3, 11, 4, 3, 5, 9, 3, 4, 5, 3, 4, 4, 3, 5, 4, 3, 7, 9, 3, 4, 7, 3
OFFSET
1,1
COMMENTS
All values are prime powers, and every prime power except 2 appears in the sequence. This can be proved using the Chinese remainder theorem.
PROG
(PARI) a(n) = my(k=2); while (issquare(Mod(-n, k)), k++); k; \\ Michel Marcus, Jul 08 2022
CROSSREFS
Cf. A139401.
Sequence in context: A163874 A165565 A033706 * A121890 A330740 A178231
KEYWORD
nonn
AUTHOR
Bruno Langlois, Jul 08 2022
STATUS
approved