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A288519
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a(n) = least k such that A080670(k) begins with n.
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1
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1, 2, 3, 41, 5, 61, 7, 83, 97, 101, 11, 127, 13, 149, 151, 163, 17, 181, 19, 2003, 22, 4, 6, 16, 10, 64, 14, 166, 29, 307, 31, 9, 27, 81, 15, 183, 21, 249, 291, 401, 41, 421, 43, 443, 457, 461, 47, 487, 491, 503, 55, 25, 53, 205, 265, 305, 35, 415, 59, 601, 61
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OFFSET
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1,2
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COMMENTS
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a(p) <= p for any prime p.
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LINKS
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EXAMPLE
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The following table shows the first values from A080670, as well as the terms that can be derived from it:
-- ---------- -------------
1 1 a(1) = 1
2 2 a(2) = 2
3 3 a(3) = 3
4 22 a(22) = 4
5 5 a(5) = 5
6 23 a(23) = 6
7 7 a(7) = 7
8 23 none
9 32 a(32) = 9
10 25 a(25) = 10
11 11 a(11) = 11
12 223 a(223) = 12
13 13 a(13) = 13
14 27 a(27) = 14
15 35 a(35) = 15
16 24 a(24) = 16
17 17 a(17) = 17
18 232 a(232) = 18
19 19 a(19) = 19
20 225 a(225) = 20
21 37 a(37) = 21
22 211 a(211) = 22, a(21) = 22
23 23 none
24 233 a(233) = 24
25 52 a(52) = 25
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MATHEMATICA
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s = Array[Flatten@ Map[IntegerDigits, DeleteCases[ Flatten@ FactorInteger@ #, 1] /. {} -> {1}] &, 10^4]; FromDigits /@ Table[ Function[k, SelectFirst[s, If[Length@# > 0, #[[1, 1]] == 1, False] &@ SequencePosition[#, k] &]]@ IntegerDigits[n], {n, 61}] (* Michael De Vlieger, Jun 11 2017 *)
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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