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A068673
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Numbers which yield primes when a 1 is prefixed or appended.
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4
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1, 3, 7, 13, 27, 31, 49, 57, 63, 81, 91, 97, 99, 103, 109, 117, 123, 129, 151, 153, 181, 187, 193, 201, 213, 231, 237, 259, 279, 297, 301, 319, 327, 367, 409, 423, 427, 439, 459, 483, 487, 493, 523, 543, 553, 559, 571, 579, 601, 609, 613, 621, 627, 657, 669
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| 57 is a term as 157 as well as 571 are primes.
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MAPLE
| i := 0:for k from 1 to 3200 do if(isprime(1+10*k) and isprime(k+10^(ceil(evalf(log(k+1)/log(10))))*1)) then s[i] := k; i := i+1; end if; end do:q := seq(s[j], j=0..i-1);
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CROSSREFS
| Sequence in context: A205521 A125898 A146928 * A140465 A080241 A098479
Adjacent sequences: A068670 A068671 A068672 * A068674 A068675 A068676
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KEYWORD
| base,easy,nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Mar 02 2002
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EXTENSIONS
| More terms from Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Mar 17 2002
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