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A068678 Numbers that yield a prime when a 9 is prefixed or suffixed to them. 0
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified January 26 11:05 EST 2020. Contains 331279 sequences. (Running on oeis4.)