Shanks, Daniel Gauss’s ternary form reduction and the 2-Sylow subgroup. (English) Zbl 0227.12002 Math. Comput. 25, 837-853 (1971). Page: −5 −4 −3 −2 −1 ±0 +1 +2 +3 +4 +5 Show Scanned Page Cited in 9 Documents MSC: 11R29 Class numbers, class groups, discriminants 11R11 Quadratic extensions PDFBibTeX XMLCite \textit{D. Shanks}, Math. Comput. 25, 837--853 (1971; Zbl 0227.12002) Full Text: DOI Online Encyclopedia of Integer Sequences: a(n) = (2^n+3)^2-8. Primes of the form (2^n+3)^2-8. Numbers k such that (2^k + 3)^2 - 8 is prime. Let G be the class group of the imaginary quadratic field Q(sqrt(-A188661(n))); the 2-Sylow subgroup of G is cyclic of order 2^a(n).