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Search: id:A089948
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| A089948 |
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First prime factor of the concatenation the first n odd primes. |
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+0
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
(list; graph; listen)
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OFFSET
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3,1
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COMMENT
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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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PROGRAM
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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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Cf. A089933.
Sequence in context: A049072 A059887 A023585 this_sequence A023583 A121278 A023587
Adjacent sequences: A089945 A089946 A089947 this_sequence A089949 A089950 A089951
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KEYWORD
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nonn
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AUTHOR
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Cino Hilliard (hillcino368(AT)gmail.com), Jan 11 2004
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