A180555 Primes that become a different prime under the mapping 6 <=> 7.

61, 71, 163, 173, 601, 619, 643, 701, 719, 743, 1609, 1621, 1709, 1721, 1861, 1871, 2689, 2789, 3361, 3371, 3671, 3761, 4261, 4271, 4363, 4373, 4603, 4621, 4651, 4703, 4721, 4751, 4861, 4871, 5563, 5573, 5641, 5669, 5683, 5741, 5779, 5783, 5869, 5879

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

Cf. A171040, A175791, A180517 thru A180559, A175789, A180560, A180561.

Sequence in context: A043993 A165287 A064229 * A039478 A109549 A139944

Adjacent sequences: A180552 A180553 A180554 * A180556 A180557 A180558

Keyword

base,nonn

Author

Zak Seidov and Robert G. Wilson v, Sep 09 2010

Status

approved