3v4l.org

run code in 150+ php & hhvm versions
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<?php $i = 1; for($f = 0; $f <= 20; $f++) { echo "F".$f." = ".intval((($f*$f-1)+$f*$f-2))."\n"; $i++; }
based on kbWTD
Output for 4.3.0 - 7.1.0
F0 = -3 F1 = -1 F2 = 5 F3 = 15 F4 = 29 F5 = 47 F6 = 69 F7 = 95 F8 = 125 F9 = 159 F10 = 197 F11 = 239 F12 = 285 F13 = 335 F14 = 389 F15 = 447 F16 = 509 F17 = 575 F18 = 645 F19 = 719 F20 = 797