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 A230370 Voids left after packing 3 curves coins patterns (3c3s type) into fountain of coins base n. 8
 0, 0, 3, 6, 13, 19, 39, 54, 66, 85, 100, 123, 141, 168, 189, 220, 244, 279, 306, 345, 375, 418, 451, 498, 534, 585, 624, 679, 721, 780, 825, 888, 936, 1003, 1054, 1125, 1179, 1254, 1311, 1390, 1450, 1533, 1596, 1683 (list; graph; refs; listen; history; text; internal format)
 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 A001399, A230267, A230276 (5-curves coins patterns); A074148, A229093, A220154 (4-curves coins patterns); A008795 (3-curves coins patterns). Sequence in context: A259583 A064349 A101965 * A285246 A147009 A318228 Adjacent sequences:  A230367 A230368 A230369 * A230371 A230372 A230373 KEYWORD nonn AUTHOR Kival Ngaokrajang, Oct 17 2013 STATUS approved

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Last modified November 14 17:12 EST 2018. Contains 317210 sequences. (Running on oeis4.)