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# TI-86: Sequence Graphing

TI-86: Sequence Graphing
The program Sequen86 plots one recursive sequence with one initial condition. The function is stored in variable y1, with x presenting y1(n-1). The initial condition is assumed to be y1(1).
This program was originally posted on ticalc.org on April 28, 2001. Link: https://www.ticalc.org/archives/files/fileinfo/186/18667.html
18 years, wow, how time flies.
TI-86 Program Sequen86
(354 bytes)
Func
FnOff
PlOff
ClLCD
DelVar(L1)
DelVar(L2)
Outpt(6,1,”Let y1 = u”)
Outpt(7,1,”Let x = n-1”)
InpSt “y1 =”, Y
St>Eq(Y,y1)
Input “Initial Cond: “,I
Input “# of Steps: “,S
{I} → U
For(N, dimL U+1, S+1, 1)
y1(U(N-1)) → U(N)
End
seq(x,x,1,S+1) → L1
U → L2
0 → xMin
S+1 → xMax
min(U) – 1 → yMin
max(U) + 1 → yMax
Plot1(1,L1,L2)
FnOff 1
Disp “L1 = n”
Pause “L2 = u”
DispG
Example:
u(n) = u(n-1)/3 + 1/4
Initial condition, u(1) = 1/5
Number of Steps: 10
Set up for Sequen86:
y1 = x/3 + 1/4

The 2019 Version
Here is an alternate version, SEQGRAPH. Use U for U(n-1) and N for n. The program allows the initial condition for any value of N.
TI-86 Program SEQGRAPH
(277 bytes)
InpSt “U1(U,N) = “,S1
St>Eq(S1,U1)
Input “N Start = “,N
Input “U0 = “,U
Input “Steps: “,S
S + 1 → dimL xList
S + 1 → dimL yList
N → xList(1)
U → yList(1)
For(I, 2, S+1)
xList(I-1) + 1 → N
N → xList(I)
yList(I-1) → U
U1 → yList(I)
End
FnOff
PlOff
PlOn 1
Plot1(1,xList,yList)
ZData
Example:
u(n) = u(n-1)/3 + 1/4
Initial condition, u(1) = 1/5
Number of Steps: 10
Set up for SEQGRAPH:
U1 = U/3 + 1/4
N Start: 1
U0 = 1/5 (initial condition)

Eddie
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