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A339141
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a(n) = reverse(10*n - a(n-1)), with n>1, a(1) = 1.
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1
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1, 91, -16, 65, -51, 111, -14, 49, 14, 68, 24, 69, 16, 421, -172, 233, -36, 612, -224, 424, -412, 236, -6, 642, -293, 355, -58, 833, -345, 546, -632, 259, 17, 323, 72, 882, -215, 595, -502, 209, 102, 813, -383, 328, 221, 932, -264, 447, 34, 664, -451
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OFFSET
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1,2
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COMMENTS
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Note that for x<0, reverse(x) is defined by -1*reverse(-x).
Starting the sequence with other numbers also gives similar-looking graphs.
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LINKS
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FORMULA
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a(n) = reverse(10*n - a(n-1)) where reverse means reverse the order of the digits.
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EXAMPLE
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For n = 2, 10*n = 10*2 = 20, 20 - a(n-1) = 20 - 1 = 19, reverse(19) = 91.
For n = 3, 10*n = 10*3 = 30, 30 - a(3-1) = 30 - 91 = -61, reverse(-61) = -16.
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MAPLE
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a:= proc(n) option remember; `if`(n<2, n, (p-> signum(p)* (f->
parse(cat(f[-i]$i=1..length(f))))(""||(abs(p))))(10*n-a(n-1)))
end:
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MATHEMATICA
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nmax=51; a[1]=1; a[n_]:=Sign[10n-a[n-1]]IntegerReverse[10n-a[n-1]]; Table[a[n], {n, nmax}] (* Stefano Spezia, Dec 05 2020 *)
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PROG
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(PARI) rev(n) = sign(n)*fromdigits(Vecrev(digits(n)));
a(n) = if (n==1, 1, rev(10*n-a(n-1))); \\ Michel Marcus, Dec 05 2020
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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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