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A165302
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a(n) is the smallest number not already in the sequence, such that the concatenation of all a(n) displays the periodic digit string 1, 2, 3, 4 (and repeat).
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3
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1, 2, 3, 4, 12, 34, 123, 41, 23, 412, 341, 234, 1234, 12341, 2341, 23412, 3412, 34123, 4123, 41234, 123412, 341234, 1234123, 412341, 234123, 4123412, 3412341, 2341234, 12341234, 123412341, 23412341, 234123412, 34123412, 341234123, 41234123, 412341234
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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EXAMPLE
| Starting from 1, 2, 3, 4, the next number must be 12 because we need to continue with a 1. But 1 is already in the sequence so we need to attach a 2 -> 12. And so on.
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MAPLE
| cyc4 := proc(n) op(n, [2, 3, 4, 1]) ; end:
A165302 := proc(n) option remember ; local k, prev, d, a ; if n = 1 then 1; else d := cyc4(procname(n-1) mod 10) ; a := d ; while true do prev := false; for k from 1 to n-1 do if procname(k) = a then prev := true; break; end if; end do; if not prev then return a; end if; d := cyc4(d) ; a := 10*a+d ; end do; end if ; end proc:
seq(A165302(n), n=1..60) ; # R. J. Mathar, Oct 16 2009
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CROSSREFS
| A165300, A165301, A165303-A165307
Sequence in context: A168047 A173446 A053350 * A117342 A126129 A102947
Adjacent sequences: A165299 A165300 A165301 * A165303 A165304 A165305
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KEYWORD
| easy,base,nonn
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AUTHOR
| Paolo P. Lava & Giorgio Balzarotti (paoloplava(AT)gmail.com), Sep 14 2009
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EXTENSIONS
| Keyword:base added, sequence extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 16 2009
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