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.
a(5) = 119 because the 5th prime is 11 and the 5th nonprime is 9.
import Data.Function (on) a253911 n = a253911_list !! (n-1) a253911_list = map read $ zipWith ((++) `on` show) a018252_list a000040_list :: [Integer] -- Reinhard Zumkeller, Feb 09 2015
nprime(n)=c=0;k=1;while(k,if(!isprime(k),c++);if(c==n,return(k));k++) vector(50,n,eval(concat(Str(prime(n)),Str(nprime(n))))) \\ Derek Orr, Feb 06 2015
a(5) = 911 because the 5th nonprime is 9 and the 5th prime is 11.
import Data.Function (on) a253911 n = a253911_list !! (n-1) a253911_list = map read $ zipWith ((++) `on` show) a018252_list a000040_list :: [Integer] -- Reinhard Zumkeller, Feb 09 2015
cncat[{a_,b_}]:=FromDigits[Flatten[IntegerDigits/@{a,b}]]; Module[ {nn=100,np,len},np = Select[Range[nn],!PrimeQ[#]&];len=Length[np];cncat/@Thread[{np,Prime[Range[len]]}]] (* Harvey P. Dale, Oct 17 2020 *)
nprime(n)=c=0; k=1; while(k, if(!isprime(k), c++); if(c==n, return(k)); k++) vector(50, n, eval(concat(Str(nprime(n)), Str(prime(n))))) \\ Derek Orr, Feb 06 2015
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