OFFSET
1,1
COMMENTS
Let points 1, 3 & 2 be placed on a straight line at intervals of 1 unit. At point 1 make a half unit circle, then at point 2 make another half circle, and maintain continuity of circumferences. Continue using this procedure at points 3, 1, 2, and so on. The form of spiral is a non-expanded loop. See illustration in links.
LINKS
Kival Ngaokrajang, Illustration of initial terms
FORMULA
G.f.: x*(4*x^4 + 7*x^3 + 2*x^2 + 7*x + 4)/((1-x)(1-x^5)) (conjectured). - Ralf Stephan, Jan 13 2014
PROG
(Small Basic)
a[1]=4
For n = 1 To 100
d1=2
m5 = math.Remainder(n+1, 5)
If m5 = 0 Or m5 = 1 Then
d1 = 4
EndIf
If m5 = 2 Or m5 = 4 Then
d1 = 7
EndIf
a[n+1]=a[n]+d1
TextWindow.Write(a[n]+", ")
EndFor
CROSSREFS
KEYWORD
nonn
AUTHOR
Kival Ngaokrajang, Jan 01 2014
STATUS
approved