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 A102270 #13 Mar 14 2024 03:58:09
%S A102270 16,8,8,8,16,8,16,16,16,8,16,32,8,8,8,8,32,8,16,64,32,8,32,8,8,128,32,
%T A102270 32,32,16,8,8,8,16,16,8,8,8,128,16,8,8,16,32,8,16,32,8,8,8,128,8,8,8,
%U A102270 16,8,64,8,8,8,16,8,16,16,16,8,8,16,32,16,8,8,8,64,32,64,16,64,8,16,32
%N A102270 2-class number of Q(sqrt(-21p)) as p runs through primes in A102269.
%H A102270 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 A102270 (Sage) [2^QuadraticField(-21*p).class_number().valuation(2) for p in Primes()[:1000] if (p%84) in [43, 67, 79]] # _Robin Visser_, Mar 13 2024
%Y A102270 Cf. A102269, A102271, A102272, A102273, A102274, A102275.
%K A102270 nonn
%O A102270 1,1
%A A102270 _N. J. A. Sloane_, Feb 19 2005
%E A102270 More terms from _Robin Visser_, Mar 13 2024