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A374155
a(n) is the least prime that is a quadratic residue modulo prime(n). First column of A373751.
1
2, 3, 5, 2, 3, 3, 2, 5, 2, 5, 2, 3, 2, 11, 2, 7, 3, 3, 17, 2, 2, 2, 3, 2, 2, 5, 2, 3, 3, 2, 2, 3, 2, 5, 5, 2, 3, 41, 2, 13, 3, 3, 2, 2, 7, 2, 5, 2, 3, 3, 2, 2, 2, 3, 2, 2, 5, 2, 3, 2, 7, 17, 7, 2, 2, 7, 5, 2, 3, 3, 2, 2, 2, 3, 5, 2, 5, 3, 2, 2, 3, 3, 2, 2, 2
OFFSET
1,1
EXAMPLE
a(38) = 41 because row 38 of A373751 starts 41, 43, 47, ..., which are the primes that are quadratic residues modulo 163.
MAPLE
a := proc(n) local a, p; a := 1; p := ithprime(n); while true do a := a + 1;
if NumberTheory:-QuadraticResidue(a, p) = 1 and isprime(a) then return a fi od end: seq(a(n), n = 1..85);
PROG
(PARI) a(n) = my(p=prime(n), q=2); while (!issquare(Mod(q, p)), q=nextprime(q+1)); q; \\ Michel Marcus, Jun 29 2024
CROSSREFS
Variant: A306530 (differs in the first 3 values).
Cf. A373751.
Sequence in context: A133907 A232931 A060084 * A361503 A265668 A273087
KEYWORD
nonn
AUTHOR
Peter Luschny, Jun 29 2024
STATUS
approved