OFFSET
1,1
COMMENTS
a(n) is the negated fundamental discriminant D < 0 with the least absolute value such that the first n primes either decompose or ramify in the imaginary quadratic field with discriminant D. See A241482 for the real quadratic field case.
EXAMPLE
(-231/2) = 1, (-231/3) = 0, (-231/5) = 1, (-231/7) = 0, (-231/11) = 0, (-231/13) = 1, so 2, 5, 13 decompose in Q[sqrt(-231)] and 3, 7, 11 ramify in Q[sqrt(-231)]. For other fundamental discriminants -231 < D < 0, at least one of 2, 3, 5, 7, 11, 13 is inert in the imaginary quadratic field with discriminant D, so a(6) = 231.
PROG
(PARI) a(n) = my(i=1); while(!isfundamental(-i)||sum(j=1, n, kronecker(-i, prime(j))==-1)!=0, i++); i
CROSSREFS
KEYWORD
nonn
AUTHOR
Jianing Song, Jan 29 2019
EXTENSIONS
a(26)-a(33) from Jinyuan Wang, Apr 06 2019
STATUS
approved