A276342 Left inverse of A274647.

0, 1, 4, 2, 203, 2597, 3, 5, 16, 14, 12, 10, 8, 6, 97, 15546, 243575589, 404450, 23, 404448, 7, 9, 11, 13, 15, 17, 56, 54, 52, 50, 631, 629, 902, 137, 135, 192, 84974, 84972, 27, 309411696, 131, 22, 20, 18, 85, 111320883, 127, 125

Offset

0,3

Comments

If A274647 is proved to be a permutation, then this is full inverse of it, and the hypothetical -1's are in that case unnecessary (or can be used as markers for yet unknown values).

Links

Hugo van der Sanden, Table of n, a(n) for n = 0..211

Robert Israel, Hugo van der Sanden, Robert Gerbicz, and Benjamin Chaffin Table of a(n) for n = 0..10000. This is based on A274647(n) for n <= 5.4*10^11. The 177 entries of -1 may correspond to values > 5.4*10^11 (first such value is at a(212)).

Formula

a(n) = index of n in A274647 or -1 if n is not present in that sequence.

For all n >= 0, a(A274647(n)) = n.

Maple

N = 10^6: # to search A274647(n) for n <= N
A[0]:= 0:B[0]:= 0:
for n from 1 to N do
  for k from 1 do
     r:= A[n-1]-k*n;
     if r > 0 and not assigned(B[r]) then
        break
     fi;
     r:= A[n-1]+k*n;
     if not assigned(B[r]) then
        break
     fi
  od;
  A[n]:= r;
  B[r]:= n;
od:
seq(B[n], n=0..100); # Robert Israel, Sep 04 2016

Prog

(Scheme) ;; Use the Scheme-code given in A274647. First one needs to compute A274647 up to some high value of n before trying to list terms of this sequence.

Crossrefs

Cf. A274647, A005132.

Sequence in context: A096683 A158903 A273148 * A350725 A152030 A072349

Adjacent sequences: A276339 A276340 A276341 * A276343 A276344 A276345

Keyword

sign

Author

Antti Karttunen, Sep 04 2016

Extensions

More terms and updated a-file from Hugo van der Sanden, Sep 05 2016

Updated a-file from Robert Gerbicz, Sep 09 2016

Updated a-file from Benjamin Chaffin, Sep 29 2016

Status

approved