OFFSET
1,2
COMMENTS
Except for the first term, all terms are coprime to 10. - Chai Wah Wu, Sep 19 2016
MAPLE
with(numtheory): P:= proc(q) local d, j, k, n, t, x; x:=4; print(0);
for n from 1 to q do d:=ilog10(n)+1; t:=0;
for k from 0 to d-1 do for j from 0 to 9 do
if isprime(trunc(n/10^(k+1))*10^(k+1)+j*10^k+(n mod 10^k))
then t:=t+1; fi; od; od;
if isprime(n) then if t-d>x then x:=t-d; print(n); fi; else
if t>x then x:=t; print(n); fi; fi; od; end: P(10^9);
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Paolo P. Lava, Sep 14 2016
EXTENSIONS
a(18)-a(19) from Chai Wah Wu, Sep 19 2016
STATUS
approved