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Search: id:A125268
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| A125268 |
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Composite integers which when written in decimal end with 1, 3, 7 or 9, and when any of the digits 0 to 9 is inserted anywhere in it (including at the beginning or end), the result is also composite. |
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+0
1
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| 25011, 52647, 72753, 122313, 168699, 251763, 283251, 324021, 598041, 783441, 804131, 826377, 837207, 924807, 1247241, 1446519, 1905759, 2514819, 2860743, 2978229, 3256639, 3461101, 3514077, 3617389, 3652443, 3905817, 3991773
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Robert G. Wilson v, Table of n, a(n) for n = 1..1401
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MATHEMATICA
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alldgt = Range@10 - 1; lst = {}; fQ[n_] := Block[{id = IntegerDigits@n, len = Floor@Log[10, n] + 1}, Union@ Flatten@ Table[PrimeQ@ FromDigits@ Insert[id, alldgt[[j]], i], {i, len}, {j, 10}] == {False}]; Do[ If[ !PrimeQ@n && Mod[n, 10] != 5 && fQ@n, Print[n]; AppendTo[lst, n]], {n, 1, 15*10^6, 2}]; lst - Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 26 2007
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CROSSREFS
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Cf. A003459.
Sequence in context: A110599 A138717 A139776 this_sequence A076583 A046709 A130615
Adjacent sequences: A125265 A125266 A125267 this_sequence A125269 A125270 A125271
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KEYWORD
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nonn
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AUTHOR
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Jack Kennedy (jack(AT)realmode.com), Jan 15 2007
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EXTENSIONS
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Corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 26 2007
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