OFFSET
1,3
COMMENTS
Refer to arrangement same as A005169: "A fountain is formed by starting with a row of coins, then stacking additional coins on top so that each new coin touches two in the previous row". The 3 curves coins patterns consist of a part of each coin circumference and forms a continuous area. There are total 4 distinct patterns. For selected pattern, I would like to call "3c3s" type as it cover 3 coins and symmetry. When packing 3c3s into fountain of coins base n, the total number of 3c3s is A008805, the coins left is A008795 and voids left is a(n). See illustration in links.
LINKS
Kival Ngaokrajang, Illustration of initial terms (V)
FORMULA
G.f.: x^3*(11*x^8 - 5*x^7 - 21*x^6 + 6*x^5 + 9*x^4 + x^2 + 3*x + 3)/((1-x)*(1-x^2)^2) (conjectured). Ralf Stephan, Oct 19 2013
PROG
(Small Basic)
a[1]=0
a[2]=0
d1[3]=3
For n=1 To 100
If n+2>=4 Then
If Math.Remainder(n+2, 2)=0 Then
d2= 2-(n+2)/2
Else
d2= (n+5)/2
EndIf
d1[n+2]=d1[n+1]+d2
EndIf
a[n+2]=a[n+1]+d1[n+2]
TextWindow.Write(a[n]+", ")
EndFor
CROSSREFS
KEYWORD
nonn
AUTHOR
Kival Ngaokrajang, Oct 17 2013
STATUS
approved