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 A253910 #10 Feb 09 2015 15:47:40 %S A253910 21,34,56,78,119,1310,1712,1914,2315,2916,3118,3720,4121,4322,4724, %T A253910 5325,5926,6127,6728,7130,7332,7933,8334,8935,9736,10138,10339,10740, %U A253910 10942,11344,12745,13146,13748,13949,14950,15151,15752,16354,16755,17356,17957,18158,19160,19362,19763,19964,21165,22366,22768,22969 %N A253910 Concatenation of n-th prime and n-th nonprime. %C A253910 Concatenate A000040(n) and A018252(n). %H A253910 Reinhard Zumkeller, <a href="/A253910/b253910.txt">Table of n, a(n) for n = 1..10000</a> %e A253910 a(5) = 119 because the 5th prime is 11 and the 5th nonprime is 9. %o A253910 (PARI) nprime(n)=c=0;k=1;while(k,if(!isprime(k),c++);if(c==n,return(k));k++) %o A253910 vector(50,n,eval(concat(Str(prime(n)),Str(nprime(n))))) \\ _Derek Orr_, Feb 06 2015 %o A253910 (Haskell) %o A253910 import Data.Function (on) %o A253910 a253911 n = a253911_list !! (n-1) %o A253910 a253911_list = map read $ %o A253910 zipWith ((++) `on` show) a018252_list a000040_list :: [Integer] %o A253910 -- _Reinhard Zumkeller_, Feb 09 2015 %Y A253910 Cf. A000040, A018252, A038530, A045532, A075110, A106582, A138821, A138822, A253911. %K A253910 nonn,base,easy %O A253910 1,1 %A A253910 _Omar E. Pol_, Feb 06 2015