A068678 Numbers that yield a prime when a 9 is prefixed or suffixed to them.

7, 19, 37, 41, 47, 71, 83, 91, 103, 127, 157, 161, 187, 199, 203, 209, 239, 257, 281, 293, 311, 349, 371, 377, 391, 413, 421, 433, 463, 467, 479, 491, 511, 539, 547, 551, 587, 619, 629, 661, 677, 689, 721, 749, 769, 787, 791, 803, 817, 859, 871, 883, 923

Offset

1,1

Links

Table of n, a(n) for n=1..53.

Example

127 is a member as both 1279 and 9127 are primes.

Maple

i := 0:for k from 1 to 3200 do if(isprime(9+10*k) and isprime(k+10^(ceil(evalf(log(k+1)/log(10))))*9)) then s[i] := k; i := i+1; end if; end do:q := seq(s[j], j=0..i-1);

Crossrefs

Cf. A068673, A068674, A068677.

Sequence in context: A154878 A124270 A298565 * A069833 A215421 A192594

Adjacent sequences: A068675 A068676 A068677 * A068679 A068680 A068681

Keyword

base,easy,nonn

Author

Amarnath Murthy, Mar 02 2002

Extensions

More terms from Sascha Kurz, Mar 17 2002

Status

approved