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Term Sum Settlement (Posted on 2015-10-29) Difficulty: 3 of 5
The sequence S1, S2,S3 ,...... is defined by:

S1 = 211, S2 = 375, S3= 420, S4 = 523, and:
Sn= Sn-1- Sn-2+ Sn-3- Sn-4

Find S531+ S753+ S975

No Solution Yet Submitted by K Sengupta    
Rating: 3.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution Well, it could have been solved manually, but... | Comment 1 of 3
The values through S(14) show the numbers cycle with a period of 10, so all the S values whose subscripts end with the same digit have the same value. However, I had written the program before finding this out:

subscript   value

5            267
6           -211
7           -375
8           -420
9           -523
10          -267
11           211
12           375
13           420
14           523
15           267
16           -211
17           -375
18           -420
19           -523
531           211
753           420
975           267
             ----
total of 3    898

so the answer is 898.

 
 Text1.Text = ""
 crlf = Chr$(13) + Chr$(10)

 
 a = 211: b = 375: c = 420: d = 523
 For j = 5 To 975
   DoEvents
   e = d - c + b - a
   a = b: b = c: c = d: d = e
   If e > 10000000 Then
     x = x
   End If
   If j < 20 Or j = 531 Or j = 753 Or j = 975 Then
     Text1.Text = Text1.Text & j & "     " & e & crlf
     If j > 20 Then tot = tot + e
   End If
   If j = 30 Then Text1.Text = Text1.Text & crlf
 Next


 Text1.Text = Text1.Text & tot & crlf & " done"
  
End Sub



  Posted by Charlie on 2015-10-29 14:31:45
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