This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A102275 #17 Mar 14 2024 05:16:35
%S A102275 8,32,8,8,8,32,64,8,16,16,64,8,16,16,16,8,32,8,8,8,32,8,16,8,8,8,8,8,
%T A102275 32,16,8,16,128,32,32,8,32,16,32,8,128,16,16,16,8,8,16,8,16,8,8,8,16,
%U A102275 16,16,8,64,8,8,16,8,8,8,8,8,8,8,16,16,16,32,16,8,16,32,16,8,8,32,16,16
%N A102275 2-class number of Q(sqrt(-21p)) as p runs through primes in A102274.
%H A102275 H. Cohn and J. C. Lagarias, <a href="http://doi.org/10.1090/S0025-5718-1983-0717716-8">On the existence of fields governing the 2-invariants of the classgroup of Q(sqrt{dp}) as p varies</a>, Math. Comp. 41 (1983), 711-730.
%o A102275 (Sage) [2^QuadraticField(-21*p).class_number().valuation(2) for p in Primes()[:1000] if (p%84) in [47, 59, 83]] # _Robin Visser_, Mar 13 2024
%Y A102275 Cf. A102269, A102270, A102271, A102272, A102273, A102274.
%K A102275 nonn
%O A102275 1,1
%A A102275 _N. J. A. Sloane_, Feb 19 2005
%E A102275 a(19) corrected and more terms from _Robin Visser_, Mar 13 2024