

A068674


Numbers which yield primes when a 3 is prefixed or appended.


11



1, 7, 11, 17, 31, 37, 59, 67, 73, 109, 119, 121, 137, 169, 187, 191, 221, 229, 259, 271, 331, 343, 359, 361, 373, 407, 413, 449, 467, 499, 511, 527, 533, 539, 541, 557, 581, 607, 613, 617, 637, 673, 701, 719, 733, 739, 767, 779, 793, 823, 851, 889, 917, 929
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..54.


EXAMPLE

73 is a term as both 373 and 733 are primes.


MAPLE

i := 0:for k from 1 to 3200 do if(isprime(3+10*k) and isprime(k+10^(ceil(evalf(log(k+1)/log(10))))*3)) then s[i] := k; i := i+1; end if; end do:q := seq(s[j], j=0..i1);


MATHEMATICA

Select[Range[930], Union[PrimeQ[FromDigits/@{Append[(x=IntegerDigits[#]), 3], Prepend[x, 3]}]]=={True} &] (* Jayanta Basu, May 20 2013 *)


CROSSREFS

Cf. A068673.
Sequence in context: A174360 A320384 A019418 * A156112 A158594 A215419
Adjacent sequences: A068671 A068672 A068673 * A068675 A068676 A068677


KEYWORD

base,easy,nonn


AUTHOR

Amarnath Murthy, Mar 02 2002


EXTENSIONS

More terms from Sascha Kurz, Mar 17 2002


STATUS

approved



