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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.
2
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
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) digitsIn(x)= { local(d); if (x==0, return(1)); d=1 + log(x)\log(10); if (10^d == x, d++, if (10^(d-1) > x, d--)); return(d) }
Concat(a, b)= { return(a*10^digitsIn(b) + b) }
{ for (n = 1, 1000, p=prime(n); q=2; while(!isprime(c=Concat(p, q)), q=nextprime(q + 1)); write("b066064.txt", n, " ", c) ) } \\ Harry J. Smith, Nov 09 2009
CROSSREFS
Sequence in context: A129800 A105184 A238056 * A163759 A190731 A348699
KEYWORD
base,nonn
AUTHOR
Reinhard Zumkeller, Dec 01 2001
STATUS
approved