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A244210 First differences of A244209. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A254246 A254375 A019684 * A019867 A144663 A197260

Adjacent sequences:  A244207 A244208 A244209 * A244211 A244212 A244213

KEYWORD

sign

AUTHOR

Kival Ngaokrajang, Jun 22 2014

STATUS

approved

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Last modified January 22 04:27 EST 2020. Contains 331133 sequences. (Running on oeis4.)