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 A257960 #36 Feb 16 2025 08:33:25
%S A257960 2,7,7,8,6,7,4,9,8,9,6,8,4,5,6,8,1,7,2,3,0,6,4,4,9,9,4,5,7,9,0,3,1,0,
%T A257960 1,4,9,0,6,9,3,6,4,2,1,1,4,6,6,7,6,5,8,8,8,3,9,1,0,1,9,3,3,2,5,5,1,9,
%U A257960 0,2,7,1,3,7,0,9,9,9,2,5,5,5,0,1,2,2,7,6,9,6,8,8,3,0,9,6,8,3,3,0,6,8,4,7,6,3,0,8,3
%N A257960 Decimal expansion of Sum_{n>=3} (-1)^n/log(log(log(n))).
%C A257960 An extremely slowly convergent series, converging in virtue of Leibniz's rule.
%H A257960 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LeibnizCriterion.html">Leibniz Criterion</a>.
%H A257960 Wikipedia, <a href="http://en.wikipedia.org/wiki/Alternating_series_test">Alternating series test</a>.
%e A257960 277.8674989684568172306449945790310149069364211466765...
%p A257960 evalf(sum((-1)^n/log(log(log(n))), n = 3..infinity), 120); # Maple 12.0 computes this expression with no problems, but later versions of Maple may have some problems with it.
%t A257960 N[NSum[(-1)^n/Log[Log[Log[n]]], {n, 3, Infinity}, AccuracyGoal -> 500, Method -> "AlternatingSigns", WorkingPrecision -> 1000], 119] (* Mathematica needs higher precision than usual to compute this series *)
%o A257960 (PARI) default(realprecision, 200); precision(sumalt(n=3, (-1)^n/log(log(log(n)))), 120) /* PARI needs higher precision than usual to compute this series */
%Y A257960 Cf. A099769, A257837, A257812, A257898.
%K A257960 nonn,cons
%O A257960 3,1
%A A257960 _Iaroslav V. Blagouchine_, May 14 2015