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A228949 Coins left when packing boomerangs into n X n coins.

%I A228949 #22 Jan 19 2019 13:26:57
%S A228949 4,3,7,13,6,13,22,9,19,31,12,25,40,15,31,49,18,37,58,21,43,67,24,49,
%T A228949 76,27,55,85,30,61,94,33,67,103,36,73,112,39,79,121,42,85,130,45,91,
%U A228949 139,48,97,148,51,103,157,54,109,166,57
%N A228949 Coins left when packing boomerangs into n X n coins.
%C A228949 The coins left after packing boomerangs into n X n coins using the same rule as A229593. See illustration in links.
%H A228949 Kival Ngaokrajang, <a href="/A228949/a228949.pdf">Illustration of initial terms</a>
%H A228949 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,2,0,0,-1).
%F A228949 G.f. -x^2*(-4-3*x-7*x^2-5*x^3+x^5) / ( (x-1)^2*(1+x+x^2)^2 ). - _R. J. Mathar_, Oct 16 2013
%t A228949 LinearRecurrence[{0,0,2,0,0,-1},{4,3,7,13,6,13},80] (* _Harvey P. Dale_, Jan 19 2019 *)
%o A228949 (Small Basic)
%o A228949 u[2]=4
%o A228949 d[3]=-1
%o A228949 d[4]=4
%o A228949 d[5]=6
%o A228949 For n=2 To 100
%o A228949   If n+1 >=6 Then
%o A228949     If Math.Remainder(n+1,3)=0 Then
%o A228949       d[n+1]=d[n-2]-6
%o A228949     Else
%o A228949       d[n+1]=d[n-2]+3
%o A228949     EndIf
%o A228949   EndIf
%o A228949   u[n+1]=u[n]+d[n+1]
%o A228949   TextWindow.Write(u[n]+", ")
%o A228949 EndFor
%Y A228949 Cf. A229593 (Boomerangs), A229598 (Voids), A017209 (trisection), A008585 (trisection), A016921 (trisection).
%K A228949 nonn,easy
%O A228949 2,1
%A A228949 _Kival Ngaokrajang_, Oct 05 2013