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 A331421 #22 Mar 02 2020 07:32:24
%S A331421 6,4,0,6,7,5,8,6,7,7,5,1,9,2,7,2,9,1,2,6,5,6,1,6,6,1,1,7,9,1,7,7,7,7,
%T A331421 7,1,9,4,5,0,7,4,9,7,2,0,0,1,9,6,4,5,0,1,9,1,0,5,3,7,9,5,7,5,5,0,4,0,
%U A331421 6,1,3,1,9,0,3,3,9,0,8,0,8,8,1,1,4,2,1
%N A331421 Decimal expansion of Sum_{n >= 2} (-1)^n/log_2(n).
%C A331421 A slowly converging series.
%H A331421 Daniel Hoyt, <a href="/A331421/a331421.py.txt">Python 3 program using series acceleration.</a>
%F A331421 Equals A002162 * A099769. - _M. F. Hasler_, Jan 31 2020
%e A331421 0.64067586775192729126561661179177777...
%o A331421 (PARI) sumalt(k=2, (-1)^k/log(k))*log(2) \\ Edited by _M. F. Hasler_, Jan 31 2020
%Y A331421 Cf. A002162, A099769, A257837, A257964, A257972, A257898, A257960, A257812.
%K A331421 nonn,cons
%O A331421 0,1
%A A331421 _Daniel Hoyt_, Jan 16 2020