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 A215633 #21 Nov 25 2020 21:00:53
%S A215633 1,0,0,3,9,0,6,2,5,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%T A215633 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
%U A215633 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1
%N A215633 Decimal expansion of Sum_{n>=1} 1/n^(n^prime(n)).
%C A215633 Is this a finite sequence? (or equivalently, is this constant rational?)
%C A215633 Unlikely: the "apparent" rationality seems to be caused by the rapid growth of the denominators; one may instead speculate that the value is transcendental. - _Joerg Arndt_, Feb 05 2013
%C A215633 The constant is approximately 257/256 (see A021260).
%e A215633 1.00390625000000000000000000... = 1 + 1/2^8 + 1/3^243 + 1/4^16384+...
%o A215633 (PARI) suminf(n=1,1/n^(n^prime(n)))
%Y A215633 Cf. A062481.
%K A215633 cons,nonn
%O A215633 1,4
%A A215633 _Balarka Sen_, Aug 18 2012