Strange plus numbers: Difference between revisions

=== Alternate solution ===

<lang delphi>program StrangePlusNumbers;

const

m = 18;

var

pr: array [0..m] of Boolean;

n, k, a, b: Integer;

q: Boolean;

begin

// prime sieve

for n := 0 to m do

begin

q := n > 1;

for k := 2 to n - 1 do

if n mod k = 0 then q := False;

pr[n] := q

end;

k := 0;

for n := 100 to 500 do

begin

a := n div 10; // first two digits

b := n mod 100; // last two digits

if pr[a div 10 + a mod 10] and

pr[b div 10 + b mod 10] then

begin

Write(n);

Inc(k);

if k mod 10 = 0 then Writeln else Write(' ')

end

end

end.</lang>

{{out}}

<pre>111 112 114 116 120 121 123 125 129 141

143 147 149 161 165 167 202 203 205 207

211 212 214 216 230 232 234 238 250 252

256 258 292 294 298 302 303 305 307 320

321 323 325 329 341 343 347 349 383 385

389 411 412 414 416 430 432 434 438 470

474 476 492 494 498</pre>