A253911 Concatenation of n-th nonprime and n-th prime.

12, 43, 65, 87, 911, 1013, 1217, 1419, 1523, 1629, 1831, 2037, 2141, 2243, 2447, 2553, 2659, 2761, 2867, 3071, 3273, 3379, 3483, 3589, 3697, 38101, 39103, 40107, 42109, 44113, 45127, 46131, 48137, 49139, 50149, 51151, 52157, 54163, 55167, 56173, 57179, 58181, 60191, 62193, 63197, 64199, 65211, 66223, 68227, 69229

Offset

1,1

Comments

Concatenate A018252(n) and A000040(n).

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Example

a(5) = 911 because the 5th nonprime is 9 and the 5th prime is 11.

Mathematica

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 *)

Prog

(PARI) 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
(Haskell)
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

Crossrefs

Cf. A000040, A018252, A038530, A045532, A075110, A106582, A138821, A138822, A253910.

Sequence in context: A238225 A088826 A125221 * A082829 A003357 A004466

Adjacent sequences: A253908 A253909 A253910 * A253912 A253913 A253914

Keyword

nonn,base,easy

Author

Omar E. Pol, Feb 06 2015

Status

approved