OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
Index to Primes, Primes that become a different prime under some mapping.
MAPLE
g:= proc(n) local L, i;
L:= subs({6=7, 7=6}, convert(n, base, 10));
add(L[i]*10^(i-1), i=1..nops(L))
end proc:
filter:= proc(x) local y;
if not isprime(x) then return false fi;
y:= g(x);
y <> x and isprime(y)
end proc:
select(filter, [seq(i, i=3..10000, 2)]); # Robert Israel, Nov 12 2019
MATHEMATICA
fQ[n_] := Block[{id = IntegerDigits@n}, (MemberQ[id, 6] || MemberQ[id, 7]) && PrimeQ[ FromDigits[ id /. {6 -> 7, 7 -> 6}] ]]; Select[ Prime@ Range@ 780, fQ]
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Zak Seidov and Robert G. Wilson v, Sep 09 2010
STATUS
approved