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 A242824 #30 Jul 20 2025 08:59:52
%S A242824 1428571,1428571428571428571428571
%N A242824 Primes formed by the initial digits of the decimal expansion of 1/7, starting at the first nonzero digit in the expansion.
%C A242824 Next term has 355 digits.
%C A242824 All terms are of the form 6x+1; a(4) has 823 digits; and there are no further terms up to and including 10000 digits. - _Harvey P. Dale_, Oct 03 2018
%H A242824 Amiram Eldar, <a href="/A242824/b242824.txt">Table of n, a(n) for n = 1..4</a>
%t A242824 Select[Table[FromDigits[PadRight[{},6n+1,{1,4,2,8,5,7}]],{n,200}],PrimeQ](* _Harvey P. Dale_, Oct 03 2018 *)
%Y A242824 Cf. A020806, A241217.
%Y A242824 Corresponding sequences for 1/k: A093676 (k=12), A242826 (k=13), A242827 (k=14), A242828 (k=17), A242833 (k=19).
%K A242824 nonn,base
%O A242824 1,1
%A A242824 _Felix Fröhlich_, May 23 2014