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A051203 Least inverse of A005210. 2
3, 1, 4, 5, 35, 10, 8, 26, 15, 38, 20, 13, 55, 78, 27, 70, 68, 53, 36, 282, 44, 73, 75, 69, 64, 34, 32, 585, 51, 30, 139, 165, 72, 121, 535, 97, 83, 253, 67, 469, 168, 61, 147, 146, 59, 93, 123, 286, 815, 1398, 112, 294, 119, 129, 347, 138, 124, 81, 144, 194, 256, 142 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

It seems likely that every number eventually appears in A005210, so this sequence is probably well-defined. - N. J. A. Sloane, Apr 16 2015

REFERENCES

Popular Computing (Calabasas, CA), Z-Sequences, Vol. 4 (No. 42, Sep 1976), pp. 12-16.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..20000

Popular Computing (Calabasas, CA), Z-Sequences, continued. Annotated and scanned copy of pages 14, 15, 16, 18 of Vol. 5 (No. 56, Nov 1977).

MAPLE

b:= proc(n) option remember;

     `if`(n<3, 1, abs(b(n-1)+2*b(n-2)-n))

    end:

a:= proc() local t, a; t, a:= 0, proc() -1 end;

      proc(n) local h;

        while a(n) = -1 do

          t:= t+1; h:= b(t);

          if a(h) = -1 then a(h):= t fi

        od; a(n)

      end

    end():

seq(a(n), n=0..100);  # Alois P. Heinz, Apr 16 2015

MATHEMATICA

nMax = 100; bMax = 2000;

b[n_] := b[n] = If[n < 3, 1, Abs[b[n-1] + 2*b[n-2] - n]];

a[n_] := (For[k = 1, k <= bMax, k++, If[b[k] == n, Return[k]]]; -1);

Table[a[n], {n, 0, nMax}] (* Jean-Fran├žois Alcover, Apr 05 2017 *)

CROSSREFS

Cf. A005210.

Sequence in context: A050057 A104449 A116416 * A243553 A286159 A194540

Adjacent sequences:  A051200 A051201 A051202 * A051204 A051205 A051206

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified March 22 12:46 EDT 2019. Contains 321421 sequences. (Running on oeis4.)