Answer: To get the largest
N-digit prime one only needs to subtract
N from 10^
N.
Jeopardy style question: What is
N?
Your task : evaluate N.
n = 3 or n = 23
997 is the last prime before 1000
99999999999999999999977 is the last prime before 100000000000000000000000
10 point 80
20 for M=1 to 200 step 2
30 if fnPrime(10^M-M) then
40 :if fnNxPrime(10^M-M+1)>10^M then print M
50 next
80 end
90 '
10000 fnOddfact(N)
10010 local K=0,P
10030 while N@2=0
10040 N=N\2
10050 K=K+1
10060 wend
10070 P=pack(N,K)
10080 return(P)
10090 '
10100 fnPrime(N)
10110 local I,X,J,Y,Q,K,T,Ans
10120 if N@2=0 then Ans=0:goto *EndPrime
10125 O=fnOddfact(N-1)
10130 Q=member(O,1)
10140 K=member(O,2)
10150 I=0
10160 repeat
10170 repeat
10180 X=fnLrand(N)
10190 until X>1
10200 J=0
10210 Y=modpow(X,Q,N)
10220 loop
10230 if or{and{J=0,Y=1},Y=N-1} then goto *ProbPrime
10240 if and{J>0,Y=1} then goto *NotPrime
10250 J=J+1
10260 if J=K then goto *NotPrime
10270 Y=(Y*Y)@N
10280 endloop
10290 *ProbPrime
10300 I=I+1
10310 until I>50
10320 Ans=1
10330 goto *EndPrime
10340 *NotPrime
10350 Ans=0
10360 *EndPrime
10370 return(Ans)
10380 '
10400 fnLrand(N)
10410 local R
10415 N=int(N)
10420 R=(int(rnd*10^(alen(N)+2)))@N
10430 return(R)
10440 '
10500 fnNxprime(X)
10510 if X@2=0 then X=X+1
10520 while fnPrime(X)=0
10530 X=X+2
10540 wend
10550 return(X)
10560 '
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Posted by Charlie
on 2018-09-23 14:35:46 |
another correct response
