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エラトステネスのふるい(210n+k)
FOR I=1 TO 10
LET N=I*10^5
PRINT N;"th prime ";NTHPRIME(N)
NEXT I
END
EXTERNAL FUNCTION NTHPRIME(M) ! M>4
LET N=M*(LOG(M)+LOG(LOG(M)))
DIM P(N),A(48)
MAT READ A
DATA 1,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,121,127,131,137,139,143,149,151,157,163,167,169,173,179,181,187,191,193,197,199,209
FOR I=0 TO INT(SQR(N)/210)
FOR J=1 TO 48
IF I=0 AND J=1 THEN LET J=2
LET K=210*I+A(J)
FOR L=K*K TO N STEP K*2
LET P(L)=1
NEXT L
NEXT J
NEXT I
LET COUNT=4 ! M>4
FOR I=0 TO INT(N/210)
FOR J=1 TO 48
IF I=0 AND J=1 THEN LET J=2
LET K=210*I+A(J)
IF P(K)=0 THEN
LET COUNT=COUNT+1
IF COUNT=M THEN
LET NTHPRIME=K
EXIT FUNCTION
END IF
END IF
NEXT J
NEXT I
END FUNCTION
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