Additive primes: Difference between revisions

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:*   the prime-numbers fandom: [https://prime-numbers.fandom.com/wiki/Additive_Primes additive primes].

=={{header|ALGOL W}}==

<lang algolw>begin % find some additive primes - primes whose digit sum is also prime %

% sets p( 1 :: n ) to a sieve of primes up to n %

procedure Eratosthenes ( logical array p( * ) ; integer value n ) ;

begin

p( 1 ) := false; p( 2 ) := true;

for i := 3 step 2 until n do p( i ) := true;

for i := 4 step 2 until n do p( i ) := false;

for i := 3 step 2 until truncate( sqrt( n ) ) do begin

integer ii; ii := i + i;

if p( i ) then for pr := i * i step ii until n do p( pr ) := false

end for_i ;

end Eratosthenes ;

integer MAX_NUMBER;

MAX_NUMBER := 500;

begin

logical array prime( 1 :: MAX_NUMBER );

integer aCount;

% sieve the primes to MAX_NUMBER %

Eratosthenes( prime, MAX_NUMBER );

% find the primes that are additive primes %

aCount := 0;

for i := 1 until MAX_NUMBER do begin

if prime( i ) then begin

integer dSum, v;

v := i;

dSum := 0;

while v > 0 do begin

dSum := dSum + v rem 10;

v := v div 10

end while_v_gt_0 ;

if prime( dSum ) then begin

writeon( i_w := 4, s_w := 0, " ", i );

aCount := aCount + 1;

if aCount rem 20 = 0 then write()

end if_prime_dSum

end if_prime_i

end for_i ;

write( i_w := 1, s_w := 0, "Found ", aCount, " additive primes below ", MAX_NUMBER )

end

end.</lang>

<pre>

2 3 5 7 11 23 29 41 43 47 61 67 83 89 101 113 131 137 139 151

157 173 179 191 193 197 199 223 227 229 241 263 269 281 283 311 313 317 331 337

353 359 373 379 397 401 409 421 443 449 461 463 467 487

Found 54 additive primes below 500

</pre>

=={{header|APL}}==