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A104719
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Concatenations of pairs of primes that differ by 10.
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7
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313, 717, 1323, 1929, 3141, 3747, 4353, 6171, 7383, 7989, 97107, 103113, 127137, 139149, 157167, 163173, 181191, 223233, 229239, 241251, 271281, 283293, 307317, 337347, 349359, 373383, 379389, 409419, 421431, 433443, 439449, 457467, 499509
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OFFSET
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1,1
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COMMENTS
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There are no primes in this sequence after a(1) = 313, as all values thereafter are divisible by 3. Semiprimes in this sequence include: a(2) = 717 = 3 * 239, a(4) = 1929 = 3 * 643, a(6) = 3747 = 3 * 1249, a(7) = 4353 = 3 * 1451, a(10) = 7989 = 3 * 2663, a(11) = 97107 = 3 * 32369, a(13) = 127137 = 3 * 42379, a(17) = 181191 = 3 * 60397, a(18) = 223233 = 3 * 74411, a(29) = 421431 = 3 * 140477, a(30) = 433443 = 3 * 144481, a(34) = 547557 = 3 * 182519, a(35) = 577587 = 3 * 192529, a(40) = 691701 = 3 * 230567, a(41) = 709719 = 3 * 236573, a(49) = 919929 = 3 * 306643, a(52) = 10091019 = 3 * 3363673.
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LINKS
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Harvey P. Dale, Table of n, a(n) for n = 1..1000
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FORMULA
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a(n) = A023203(n) concatenated with A023203(n)+10.
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EXAMPLE
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Primes 3 and 13 differ by 10.
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MATHEMATICA
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FromDigits[Join[IntegerDigits[#], IntegerDigits[#+10]]]&/@Select[ Prime[ Range[ 100]], PrimeQ[ #+10]&] (* Harvey P. Dale, Jun 14 2015 *)
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CROSSREFS
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Cf. A000040, A001358, A023202, A103195, A103206, A104718.
Sequence in context: A142951 A176571 A142628 * A087364 A090514 A068681
Adjacent sequences: A104716 A104717 A104718 * A104720 A104721 A104722
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KEYWORD
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base,easy,nonn
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AUTHOR
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Jonathan Vos Post and Parthasarathy Nambi, Mar 20 2005
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STATUS
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approved
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