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A089948
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Smallest prime factor of the concatenation of the first n odd primes.
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1
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3, 5, 3, 13, 3, 23, 3, 11, 7, 13, 3, 137, 3, 19, 41, 3, 29, 1087, 7, 23, 3, 641, 7, 79, 124516914725653, 1254907, 983, 691, 19, 9656610616812422838401, 11, 3, 19, 3, 4951, 83404036302541, 3, 372707, 53, 3, 17, 3, 6073, 3, 11, 37, 3
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OFFSET
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1,1
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COMMENTS
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3 is the only number < 10000 whose concatenation of odd primes is prime. Conjecture: Beyond 3 the concatenation of odd primes produce only composite numbers.
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LINKS
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MATHEMATICA
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Join[{x=3}, Table[First[First/@FactorInteger[x=FromDigits[Flatten[IntegerDigits[{x, Prime[n]}]]]]], {n, 3, 30}]] (* Jayanta Basu, Jun 04 2013 *)
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PROG
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(PARI) factorconcat(n) = { y=""; forprime(x=3, n, y=concat(Str(y), Str(x)); z=eval(y); a = component(factor(z), 1); print1(a[1]", ") ) }
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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