Source code in the action! programming language

DEFINE NOTLUDIC="0"
DEFINE LUDIC="1"
DEFINE UNKNOWN="2"

PROC LudicSieve(BYTE ARRAY a INT count)
  INT i,j,k

  SetBlock(a,count,UNKNOWN)
  a(0)=NOTLUDIC
  a(1)=LUDIC

  i=2
  WHILE i
  DO
    IF a(i)=UNKNOWN THEN
      a(i)=LUDIC
      j=i k=0
      WHILE j
      DO
        IF a(j)=UNKNOWN THEN
          k==+1
          IF k=i THEN
            a(j)=NOTLUDIC
            k=0
          FI
        FI
        j==+1
      OD
    FI
    i==+1
    Poke(77,0) ;turn off the attract mode
  OD
RETURN

PROC PrintLudicNumbers(BYTE ARRAY a INT count,first,last)
  INT i,j

  i=1 j=0
  WHILE i
  DO
    IF a(i)=LUDIC THEN
      IF j>=first THEN
        PrintI(i) Put(32)
      FI
      j==+1
    FI
    i==+1
  OD
  PutE() PutE()
RETURN

INT FUNC CountLudicNumbers(BYTE ARRAY a INT max)
  INT i,res

  res=0
  FOR i=1 TO max
  DO
    IF a(i)=LUDIC THEN
      res==+1
    FI
  OD
RETURN (res)

PROC PrintLudicTriplets(BYTE ARRAY a INT max)
  INT i,j

  j=0
  FOR i=0 TO max-6
  DO
    IF a(i)=LUDIC AND a(i+2)=LUDIC AND a(i+6)=LUDIC THEN
      j==+1
      PrintF("%I. %I-%I-%I%E",j,i,i+2,i+6)
    FI
  OD
RETURN

PROC Main()
  DEFINE COUNT="22000"
  BYTE ARRAY lud(COUNT+1)
  INT i,n

  PrintE("Please wait...")
  LudicSieve(lud,COUNT+1)
  Put(125) PutE() ;clear the screen

  PrintE("First 25 ludic numbers:")
  PrintLudicNumbers(lud,COUNT+1,0,24)

  n=CountLudicNumbers(lud,1000)
  PrintF("There are %I ludic numbers <= 1000%E%E",n)

  PrintE("2000'th..2005'th ludic numbers:")
  PrintLudicNumbers(lud,COUNT+1,1999,2004)

  PrintE("Ludic triplets below 250")
  PrintLudicTriplets(lud,249)
RETURN