Rosetta Code

Palindromic primes: Difference between revisions

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Palindromic primes (view source)

Revision as of 17:38, 8 August 2021

182 bytes removed ,  2 years ago
m
→‎{{header|REXX}}: changed the GENP subroutine.
(Added Sidef)
m (→‎{{header|REXX}}: changed the GENP subroutine.)
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@.1=2; @.2=3; @.3=5; @.4=7; @.5=11 /*define some low primes. */
!.2=1; !.3=1; !.5=1; !.7=1; !.11=1 /* " " " " flags. */
#=5; ssq.#= @.# **2 /*number of primes so far; prime². */
/* [↓] generate more primes ≤ high.*/
do j=@.#+2 by 2 to hip /*find odd primes from here on. */
parse var j '' -1 _; if if _==5 then iterate /*J divisible÷ by 5? (right digdigit).*/
if j//3==0 then iterate; if j// 37==0 then iterate /*" " " 3? J ÷ by 7? */
do k=5 while sq.k<=j if j// 7==0 then iterate /*" " " 7? [↓] divide by the known odd primes.*/
/* [↑] the above 3 lines saves time.*/
do k=5 while s.k<=j /* [↓] divide by the known odd primes.*/
if j // @.k == 0 then iterate j /*Is J ÷ X? Then not prime. ___ */
end /*k*/ /* [↑] only process numbers ≤ √ J */
#= #+1; @.#= j; ssq.#= j*j; !.j= 1 /*bump # of Ps; assign next P; P²; P# */
end /*j*/; return</lang>
{{out|output|text=&nbsp; when using the default inputs:}}
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