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Search: id:A071620
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| A071620 |
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Concatenation of first n entries (digits) of A007376 is prime. |
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1
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OFFSET
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1,1
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COMMENT
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From a question from Lekraj Beedassy (blekraj(AT)yahoo.com), Jun 20 2002 in A072125.
If instead, we look for n's such that concatenation of first n positive integers of A033307 is prime, there are no n's <=1500.
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MATHEMATICA
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f[0] = 0; f[n_Integer] := 10^(Floor[Log[10, n]] + 1)*f[n - 1] + n; Do[ If[ PrimeQ[ FromDigits[ Take[ IntegerDigits[ f[n]], n]]], Print[n]], {n, 1, 3000}]
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CROSSREFS
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Cf. A007376 & A033307.
Sequence in context: A084278 A069207 A136197 this_sequence A053690 A031028 A115603
Adjacent sequences: A071617 A071618 A071619 this_sequence A071621 A071622 A071623
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KEYWORD
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hard,nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 21 2002
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