(30b) Perrin Sequence & a Quick Prime Test

11202014, 04:44 PM
(This post was last modified: 06152017 01:24 PM by Gene.)
Post: #1




(30b) Perrin Sequence & a Quick Prime Test
Perrin sequence for integer input > 0
0 P0 1 Lbl 01 2 STO 2 3 3 4 STO 1 5 1 6 +/ 7 = 8 1 9 = 10 1 11 +/ 12 = 13 Lbl 00 14 RCL 1 15 R↓ 16 + 17 STO 1 18 R↓ 19 Swap 20 1 21 STO 2 22 RCL* 2 23 GT 00 24 RCL 1 25 RTN The Perrin sequence beginning at index 1 is 0, 2, 3, 2, 5, 5, 7, 10, 12, 17, 22, 29, 39, 51, 68, 90, 119, 158, 209, 277, 367, 486 … The programme returns exact values for indices 1 to 98, thereafter approximate. A pleasant attribute of the series is that if the index divides the indexed value with nonzero remainder the index is not prime. Accordingly, a quick prime test follows: 0 P1 1 STO 3 2 Call01 3 RCL/ 3 4 Math 5 Up 6 Input 7 0 8 ?= 9 RTN All primes in the range 2 to 98 are correctly identified with a 1 returned, as are all nonprimes shown by a 0. 

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