A244210 First differences of A244209.

8, -4, 8, 0, 4, 0, 16, -12, 8, 0, 12, -8, 8, 4, 4, 4, 16, -16, 4, 0, 16, -12, 8, 8, 12, -8, 8, -4, 0, 0, 28, -20, 20, -8, 8, 4, 0, 0, -4, 0, 32, -4, 0, -8, 12, -8, 8, 4, 20, -20, 16, 0, -4, 0, 24, -20, 8, 8, 20, -24, 16, 12, -16, 8, 12, -4, 20, -8, 8, -28, 32, 0, -4, -8, 32

Offset

1,1

Comments

All terms are even with some numbers missing, e.g., 2, 6, 10, 14, 18, 22, 26, 30, ... ,. For the first 1000 terms, the maximum is 136 at a(881) and the minimum is -156 at a(814).

Links

Kival Ngaokrajang, Table of n, a(n) for n = 1..1000

Prog

(Small Basic)
For n=1 to 200
  count=0
  row=math.Ceiling((n+1)/2)-1
    for i=0 To row
      for j=0 To row
        x=math.power(4*i*i+4*j*j, 1/2)
        c1=-x+1-n
        c2=-x-1+n
        c3=-x+1+n
        c4=x+1+n
        If x>0 and c1*c2*c3*c4>0 then
          c=(1/x)*math.Power(c1*c2*c3*c4, 1/2)
        Else
          c=0
        EndIf
        If c>0 Then
          count=count+1
        EndIf
      EndFor
    EndFor
  If Math.Remainder(n, 2)=0 Then
    circle[n]=4*(count-2)+4
  Else
    circle[n]=4*count
  EndIf
  If n > 1 Then
    TextWindow.Write(circle[n]-circle[n-1]+", ")
  EndIf
EndFor

Crossrefs

Cf. A244209.

Sequence in context: A254375 A359837 A019684 * A019867 A144663 A197260

Adjacent sequences: A244207 A244208 A244209 * A244211 A244212 A244213

Keyword

sign

Author

Kival Ngaokrajang, Jun 22 2014

Status

approved