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COMMENTS
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Starting with other primes we find:
3, 31, 101, 103, 307, 701, 1009, 9001, 10007,.. or
5, 53, 307, 701, 1009, 9001, 10007, 70001, 10000.... or
7, 71, 101, 103, 307, 701, 1009, 9001, 10007, 70001 .. or
11, 13, 31, 101, 103, 307, 701, 1009, 9001,.. or
13, 31, 101, 103, 307, 701, 1009, 9001,.. or
17, 71, 101, 103, 307, 701, 1009, 9001, 10007,.. or
19, 97, 701, 1009, 9001, 10007, 70001, 100003,.. (End)
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MAPLE
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option remember;
local a, sdig, adgs, ad ;
if n = 1 then
2;
else
sdig := procname(n-1) mod 10 ;
a := nextprime(procname(n-1)) ;
while true do
adgs := convert(a, base, 10) ;
ad := op(-1, adgs) ;
if op(-1, adgs) = sdig then
if isprime(a) then
return a;
end if;
elif ad > sdig then
a := sdig*10^nops(adgs) ;
elif ad < sdig then
a := sdig*10^(nops(adgs)-1) ;
end if;
a := nextprime(a) ;
end do:
end if;
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