A104663 Position of n in A105822.

1, 2, 3, 6, 4, 11, 8, 5, 26, 9, 12, 7, 15, 17, 33, 43, 10, 25, 16, 19, 13, 32, 39, 21, 61, 175, 22, 20, 57, 37, 95, 14, 18, 50, 27, 40, 34, 110, 29, 24, 171, 23, 64, 28, 46, 203, 45, 31, 137, 91, 134, 35, 58, 30, 90, 54, 69, 106, 38, 73, 360, 296, 67, 88, 48, 70, 526, 109, 124

Offset: 1

Author

Zak Seidov, Apr 22 2005

Keywords

• nonn

Comments

Is A105822 a permutation of the positive integers?

Links

• Ivan Neretin, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A105822.

Programs

Maple

N:= 1000: # to go up to the first entry missing in A105822(1 .. N)
A:= 'A':
a[1]:= 1: a[2]:= 2:
A[1]:= 1: A[2]:= 2:
for n from 3 to N do
  ds:= map(t -> rhs(op(t)), [msolve(x^2=a[n-1]^2, 4*a[n-2])]);
  xmin:= infinity;
  for d in ds do
    found:= false;
    for y from floor((a[n-1]-d)/(4*a[n-2]))+1 do
      xy:= 4*a[n-2]*y + d;
      cand:= (xy^2 - a[n-1]^2)/(4*a[n-2]);
      if cand >= xmin then found:= false; break fi;
      if not assigned(A[cand]) then found:= true; break fi;
    od:
    if found then xmin:= cand;  fi;
  od:
  a[n]:= xmin;
  A[xmin]:= n;
od:
M:= min(select(t -> not assigned(A[t]), [$1..N+1])):
seq(A[i],i=1..M-1); # Robert Israel, May 11 2015

Extensions

Definition corrected by N. J. A. Sloane, Aug 29 2008