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 A019566 The differences 1-1, 21-12, 321-123, ..., 10987654321-12345678910, 1110987654321-1234567891011, etc. 5
 0, 9, 198, 3087, 41976, 530865, 6419754, 75308643, 864197532, -1358024589, -123580236690, -2345801446791, 775432077543108, 178553219976533007, 27956332009875522906, 3805734210999774512805, 481583522109989673502704, 58259362312008979572492603 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS All terms are divisible by 9, cf. A083449. There is an increasingly longer subsequence of negative terms starting at each power of 10, namely for indices n = 10..12, 100..123, 1000..1234, etc. - M. F. Hasler, Nov 02 2016 Gupta (1988) calls these "unique numbers". REFERENCES S. S. Gupta, Unique Numbers, Science Today, Jan 01 1988, India. LINKS Alois P. Heinz, Table of n, a(n) for n = 1..350 Shyam Sunder Gupta, Unique Numbers FORMULA a(n) = A000422(n) - A007908(n) = 9*A083449(n). MAPLE u:= proc(n) u(n):= `if`(n=1, 1, parse(cat(u(n-1), n))) end: d:= proc(n) d(n):= `if`(n=1, 1, parse(cat(n, d(n-1)))) end: a:= n-> d(n)-u(n): seq(a(n), n=1..20);  # Alois P. Heinz, Dec 06 2014 MATHEMATICA f[n_] := Block[ {a = "", k = 1}, While[k < n + 1, a = StringJoin[ ToString[k], a]; k++ ]; Return[ ToExpression[a] - ToExpression[ StringReverse[a]]]]; Table[ f[n], {n, 1, 17} ] PROG (PARI) A = vector(25); c = 1; f = 1; for (i = 2, 9, c = 10*c + i; f = f + i*10^(i - 1); A[i] = (f - c)); for (i = 10, 25, c = 100*c + i; f = f + i*10^(2*i - 11);; A[i] = (f - c)); A \\ - David Wasserman, Nov 09 2004 (PARI) apply( {A019566(n)=A000422(n)-A007908(n)}, [1..22]) \\ Replacing code from Jan 13 2013, following a comment from Nov 02 2016. - M. F. Hasler, Nov 07 2020 CROSSREFS Cf. A000422, A007908. Sequence in context: A291974 A180778 A110807 * A338226 A157563 A003026 Adjacent sequences:  A019563 A019564 A019565 * A019567 A019568 A019569 KEYWORD sign,base,easy AUTHOR EXTENSIONS More terms from Robert G. Wilson v, Jan 11 2002 More terms from David Wasserman, Nov 09 2004 Edited by N. J. A. Sloane, Nov 22 2020 STATUS approved

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Last modified April 16 12:25 EDT 2021. Contains 343037 sequences. (Running on oeis4.)