A066064 a(n) = p.q in decimal notation where p = prime(n) and q is the smallest prime (A066065(n)) such that the concatenation p.q is a prime.

23, 37, 53, 73, 113, 137, 173, 193, 233, 293, 313, 373, 4111, 433, 4723, 5323, 593, 613, 673, 7129, 733, 797, 8311, 8923, 977, 1013, 1033, 10711, 1093, 11311, 1277, 13147, 1373, 13913, 1493, 15131, 15731, 1637, 16729, 1733, 17911, 18119, 1913

Offset

1,1

Links

Harry J. Smith, Table of n, a(n) for n = 1..1000

Example

A000040(2) = 3 and as 32, 33 and 35 are composite, the next prime 7 = A066065(2) yields a(2) = 37.

Mathematica

Table[Block[{q = 3, d = IntegerDigits[p], k}, While[! PrimeQ@ Set[k, FromDigits[Join[d, IntegerDigits[q]]]], q = NextPrime@ q]; k], {p, Prime@ Range@ 43}] (* Michael De Vlieger, Jun 19 2018 *)

Prog

(PARI) a(n) = { my(p=prime(n)); forprime(q=3, oo, my(c=p*10^(logint(q, 10)+1) + q); if(isprime(c), return(c))) } \\ Harry J. Smith, Nov 09 2009

Crossrefs

Cf. A066065.

Sequence in context: A129800 A105184 A238056 * A163759 A190731 A348699

Adjacent sequences: A066061 A066062 A066063 * A066065 A066066 A066067

Keyword

base,nonn

Author

Reinhard Zumkeller, Dec 01 2001

Status

approved