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Search: id:A104644
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| A104644 |
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a(n) is the smallest prime divisor of the number obtained from concatenation of the first n primes. |
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+0
4
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| 2, 23, 5, 2357, 7, 23, 11, 7, 61, 3, 17, 7, 25391, 6899, 1597, 3, 17, 3, 1019, 3, 17, 211, 41378209, 3, 479, 3, 262343078386137703, 3, 107, 3, 643, 3, 7, 3, 13, 3, 107069, 7, 14733071537, 3, 61911427, 3, 13, 3, 31, 3, 11, 59, 7, 647, 31, 3, 13, 3, 31517, 43, 3, 19
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Dario Alejandro Alpern, Factorization using the Elliptic Curve Method.
Hisanori Mishima, Smarandache consecutive prime sequences (n = 1 to 100).
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EXAMPLE
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n=5, concatenation of {2,3,5,7,11} is 235711=7*151*223, smallest prime
factor is a(5)=7.
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MATHEMATICA
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<<NumberTheory`NumberTheoryFunctions` sz[x_] :=FromDigits[Flatten[Table[IntegerDigits[Prime[j]], {j, 1, x}], 1]] Table[Min[PrimeFactorList[sz[w]]], {w, 1, 28}]
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CROSSREFS
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Cf. A019158, A074809.
Sequence in context: A114008 A110354 A120713 this_sequence A128365 A016837 A084323
Adjacent sequences: A104641 A104642 A104643 this_sequence A104645 A104646 A104647
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Mar 18 2005
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EXTENSIONS
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a(29) onward from Robert G. Wilson v (rgwv(AT)rgwv.com), Mar 18 2005
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