perplexus.info :: Numbers : Big, super and prime

Big, super and prime (Posted on 2010-10-20)

A superprime is an integer such that all its left-to-right initial segments are prime (e.g. 7331 whose segments are 7, 73, 733, and 7331, all prime).
There is a largest superprime.

Find it.

Source: USA Computing Olympiad, Feb 1995.

No Solution Yet Submitted by Ady TZIDON

Rating: 3.0000 (2 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)

re(2): Another method. -- solution for that Euler problem 37

| Comment 5 of 8 |

(In reply to re: Another method. by Daniel)

list
   10     Pr=2:gosub *Addon
   20     Pr=3:gosub *Addon
   30     Pr=5:gosub *Addon
   40     Pr=7:gosub *Addon
   50     end
   60
   70     *Addon
   75     local Dig
   80     for Dig=3 to 9 step 2
   90       Pr=Pr*10+Dig
100       Digs=int(log(Pr)/log(10))+1
105       Good=1
110       for St=0 to Digs-1
120         Tst=Pr-(Pr\(10^(Digs-St)))*10^(Digs-St)
130         if prmdiv(Tst)<>Tst then Good=0
140       next
200       if prmdiv(Pr)=Pr and Good=1 then
210       :print Pr
220       :gosub *Addon
230       if prmdiv(Pr)=0 then print "**":end
240       Pr=Pr\10
250     next Dig
260     return
OK
run
23
37
373
53
73
OK

Posted by Charlie on 2010-10-20 15:18:20

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