login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Least k such that the class number of quadratic order of discriminant D=-4k equals p, where p runs through the primes.
0

%I #10 Apr 03 2020 07:54:27

%S 5,11,47,71,167,191,383,311,647,887,719,1487,1151,1847,3023,2711,2399,

%T 3863,3719,5471,2999,4391,3911,6311,5519,5879,13799,8231,5711,8039,

%U 19463,12671,15287,9239,17783,22727,25847,40039,15671,14159,17519,14759,22271,26591

%N Least k such that the class number of quadratic order of discriminant D=-4k equals p, where p runs through the primes.

%o (PARI) a(n) = {my(k=1, p=prime(n)); while(abs(p-qfbclassno(-4*k))>0,k++); k; }

%Y Cf. A000003.

%K nonn

%O 1,1

%A _Benoit Cloitre_, Feb 01 2003

%E More terms from _Jinyuan Wang_, Apr 03 2020