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 A176942 #67 Feb 16 2025 08:33:12
%S A176942 1234567891,12345678910111,123456789101112131415161
%N A176942 Champernowne primes.
%C A176942 Primes formed from an initial portion 1234... of the infinite string 12345678910111213... of the concatenation of all positive integers (decimal digits of the Champernowne constant).
%C A176942 From _Eric W. Weisstein_, Jul 15 2013: (Start)
%C A176942 The next terms are too big to display:
%C A176942 a(4) = 123456789...1121131141 (235 digits)
%C A176942 a(5) = 123456789...6896997097 (2804 digits)
%C A176942 a(6) = 12345...13611362136313 (4347 digits)
%C A176942 a(7) = 123456789...9709971097 (37735 digits)
%C A176942 a(8) has more than 37800 digits. (End)
%C A176942 a(8) has more than 140000 digits. - _Tyler Busby_, Feb 12 2023
%D A176942 R. W. Stephan, Factors and primes in two Smarandache sequences.
%H A176942 Eric W. Weisstein, <a href="/A176942/b176942.txt">Table of n, a(n) for n = 1..6</a>
%H A176942 Eric W. Weisstein, <a href="/A176942/a176942.txt">Table of n, a(n) for n = 1..7</a> (an a-file)
%H A176942 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ChampernowneConstant.html">Champernowne Constant</a>
%H A176942 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ConstantPrimes.html">Constant Primes</a>
%H A176942 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/IntegerSequencePrimes.html">Integer Sequence Primes</a>
%H A176942 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SmarandachePrime.html">Smarandache Prime</a>
%t A176942 With[{no=500},FromDigits/@Select[Table[Take[Flatten[IntegerDigits/@Range[no]],n],{n,no}],PrimeQ[FromDigits[#]]&]] (* _Harvey P. Dale_, Feb 06 2011 *)
%t A176942 Select[Table[Floor[N[ChampernowneNumber[10], n]*10^n], {n, 24}], PrimeQ] (* _Arkadiusz Wesolowski_, May 10 2012 *)
%Y A176942 Cf. A007908, A058183, A073175, A053546.
%Y A176942 Cf. A007376 (infinite Barbier word = almost-natural numbers: write n in base 10 and juxtapose digits).
%Y A176942 Cf. A033307 (decimal expansion of Champernowne constant).
%Y A176942 Cf. A071620 (number of digits in the n-th Champernowne prime).
%Y A176942 See A265043 for where to end the string of numbers that are being concatenated in order to get the n-th prime.
%K A176942 base,nonn
%O A176942 1,1
%A A176942 _Marco Ripà_, Jan 27 2011