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エラトステネスのふるい(30n+k)
LET N=3
FOR I=0 TO 9
LET S=ERATOS(I*10^N,(I+1)*10^N)
LET SUM=SUM+S
PRINT I*10^N+1;"～";(I+1)*10^N;":";S;SUM
NEXT I
END
EXTERNAL FUNCTION ERATOS(S,E) ! S>=0 , S<E , E>5
DIM P(0 TO E-S+1),A(8)
MAT READ A
DATA 1,7,11,13,17,19,23,29
FOR I=0 TO INT(SQR(E)/30)
FOR J=1 TO 8
IF I=0 AND J=1 THEN LET J=2
LET K=30*I+A(J)
LET KK=INT(S/K)*K
IF KK=0 THEN LET KK=K*K
IF KK < S THEN LET KK=KK+K
IF MOD(KK,K)<>0 THEN LET KK=KK+K
IF MOD(INT(KK/K),2)=0 THEN LET KK=KK+K
FOR L=KK TO E STEP K*2
LET P(L-S)=1
NEXT L
NEXT J
NEXT I
IF S<=5 THEN LET COUNT=1
IF S<=3 THEN LET COUNT=2
IF S<=2 THEN LET COUNT=3
FOR I=INT(S/30) TO INT(E/30)
FOR J=1 TO 8
IF I=0 AND J=1 THEN LET J=2
LET K=30*I+A(J)
IF K>E THEN EXIT FOR
IF K>=S AND P(K-S)=0 THEN LET COUNT=COUNT+1
NEXT J
NEXT I
LET ERATOS=COUNT
END FUNCTION
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