A180549 - OEIS

A180549

Primes that become a different prime under the mapping 4 <=> 8.

43, 83, 241, 281, 349, 389, 409, 421, 439, 443, 457, 463, 547, 587, 643, 683, 809, 821, 839, 857, 863, 883, 1249, 1289, 1423, 1471, 1487, 1543, 1583, 1747, 1787, 1823, 1847, 1871, 2341, 2381, 2437, 2447, 2647, 2687, 2749, 2789, 2837, 2887, 3049, 3089, 3433

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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

filter:= proc(n) local L, Lp, i;

if not isprime(n) then return false fi;

L:= convert(n, base, 10);

Lp:= subs({4=8, 8=4}, L);

if L = Lp then return false fi;

isprime(add(Lp[i]*10^(i-1), i=1..nops(L)));

end proc:

select(filter, [seq(i, i=3..10000, 2)]); # Robert Israel, Nov 27 2019

MATHEMATICA

fQ[n_] := Block[{id = IntegerDigits@n}, (MemberQ[id, 4] || MemberQ[id, 8]) && PrimeQ[ FromDigits[ id /. {4 -> 8, 8 -> 4}] ]]; Select[ Prime@ Range@ 490, fQ]

CROSSREFS

Cf. A171045, A175791, A180517 thru A180559, A175789, A180560, A180561.

Sequence in context: A139982 A171252 A119487 * A247436 A063351 A065874

Adjacent sequences: A180546 A180547 A180548 * A180550 A180551 A180552

KEYWORD

base,nonn

AUTHOR

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

STATUS

approved