Find prime n such that reversed n is also prime: Difference between revisions
Find prime n such that reversed n is also prime (view source)
Revision as of 04:43, 9 January 2022
, 2 years agoAdd PL/I
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389</pre>
=={{header|PL/I}}==
<lang pli>reversePrimes: procedure options(main);
declare prime(1:999) bit;
sieve: procedure;
declare (i,j,hi) fixed;
hi = hbound(prime,1);
prime(1) = '0'b;
do i=2 to hi; prime(i) = '1'b; end;
do i=2 to sqrt(hi);
do j=i*i to hi by i; prime(j) = '0'b; end;
end;
end sieve;
reverse: procedure(nn) returns(fixed);
declare (n, nn, r) fixed;
r=0;
do n=nn repeat(n/10) while (n>0);
r = 10*r + mod(n,10);
end;
return(r);
end reverse;
declare (n, found) fixed;
call sieve;
found = 0;
do n=1 to 499;
if prime(n) & prime(reverse(n)) then do;
put edit(n) (F(4));
found = found + 1;
if mod(found,20) = 0 then put skip;
end;
end;
put skip list('Reverse primes found:',found);
end reversePrimes;</lang>
{{out}}
<pre> 2 3 5 7 11 13 17 31 37 71 73 79 97 101 107 113 131 149 151 157
167 179 181 191 199 311 313 337 347 353 359 373 383 389
Reverse primes found: 34</pre>
=={{header|Quackery}}==
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