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 A175789 Primes that become another prime under the map 8 <-> 9 (acting on the decimal digits). 49
 181, 191, 283, 293, 787, 797, 811, 853, 877, 881, 887, 911, 953, 977, 991, 997, 1087, 1097, 1483, 1493, 1801, 1831, 1873, 1901, 1931, 1973, 2287, 2297, 2383, 2393, 2683, 2693, 2803, 2857, 2903, 2957, 3181, 3191, 3583, 3593, 3823, 3847, 3923, 3947, 4483 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 EXAMPLE 283 is in the sequence because changing the 8 to a 9 it becomes 293, a different prime. Likewise 293 is also in the sequence. 383 is not in the sequence because changing the 8 to a 9 it becomes 393, which is thrice 131. MAPLE N:= 1000000: # to get all entries <= N F:= proc(n) local L, R, i;   if not isprime(n) then return false end if;   L:= convert(n, base, 10);   R:= subs([8=9, 9=8], L);   if R = L then return false end if;   isprime(add(R[i]*10^(i-1), i=1..nops(R))) end proc: select(F, [seq(2*i+1, i=1..floor((N-1)/2))]); # Robert Israel, Feb 11 2013 MATHEMATICA Reap[Do[p = Prime[n]; id = IntegerDigits[p]; id2 = id /. {9 -> 8, 8 -> 9}; If[PrimeQ[fd = FromDigits[id2]]&& fd != p, Sow[p]], {n, 2000}]][[2, 1]]; (* Seidov, corrected by Wouter Meeussen, Feb 10 2013 *) fQ[n_] := Block[{id = IntegerDigits@n}, (MemberQ[id, 8] || MemberQ[id, 9]) && PrimeQ[ FromDigits[id /. {8 -> 9, 9 -> 8}] ]]; Select[ Prime@ Range@ 609, fQ] (* Robert G. Wilson v, Sep 06 2010 *) PROG (PARI) is_A175789(n)={my(d=digits(n)); d != (d=apply(t->bitxor(t, t>7), d)) & isprime( sum(i=1, #d, d[i]*10^(#d-i))) & isprime(n)} \\ - M. F. Hasler, Feb 11 2013 CROSSREFS Cf. A171057. Sequence in context: A253432 A218977 A253439 * A157747 A253156 A139649 Adjacent sequences:  A175786 A175787 A175788 * A175790 A175791 A175792 KEYWORD base,nonn AUTHOR Zak Seidov, Sep 05 2010 STATUS approved

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Last modified October 20 22:44 EDT 2019. Contains 328291 sequences. (Running on oeis4.)