A105347 Concatenation of the largest and the smallest n-digit primes (in that order).

72, 9711, 997101, 99731009, 9999110007, 999983100003, 99999911000003, 9999998910000019, 999999937100000007, 99999999671000000007, 9999999997710000000019, 999999999989100000000003, 99999999999711000000000039, 9999999999997310000000000037

Offset

1,1

Links

Table of n, a(n) for n=1..14.

Chris Caldwell, The First 10,000 Primes.

Example

The largest and smallest 1-digit primes are 7 and 2, so the first term is 72.
The largest and smallest 2-digit primes are 97 and 11, so the second term is 9711.

Maple

for n from 0 to 30 do for m from 1 to 10^(n+1)-1 do if isprime(10^(n+1) - m) then printf(`%d`, 10^(n+1)-m); break; fi: od: for m from 1 to 10^(n+1)-1 do if isprime(10^n + m) then printf(`%d`, 10^n+m); break; fi: od: printf(`, `): od: # James A. Sellers, May 02 2005

Mathematica

Table[FromDigits[Join[IntegerDigits[NextPrime[10^n, -1]], IntegerDigits[NextPrime[10^(n-1)]]]], {n, 14}] (* James C. McMahon, Jan 22 2024 *)

Crossrefs

Cf. A104206.

Sequence in context: A178635 A271189 A093272 * A093236 A146500 A271190

Adjacent sequences: A105344 A105345 A105346 * A105348 A105349 A105350

Keyword

nonn,base

Author

Parthasarathy Nambi, Apr 30 2005

Extensions

More terms from James A. Sellers, May 02 2005

Offset corrected by Michel Marcus, Aug 18 2017

a(13)-a(14) from James C. McMahon, Jan 22 2024

Status

approved