A288519 a(n) = least k such that A080670(k) begins with n.
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
Offset: 1
Examples
The following table shows the first values from A080670, as well as the terms that can be derived from it: k A080670(k) Derived terms -- ---------- ------------- 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
Links
- Rémy Sigrist, Table of n, a(n) for n = 1..10000
- Rémy Sigrist, Scatterplot of the first 1000000 terms
- Rémy Sigrist, PARI program for A288519
Programs
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Mathematica
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 *)
Comments