A088866 Primes where flipping 6 and 9 is also prime.

97, 67, 193, 197, 163, 167, 293, 263, 397, 367, 491, 461, 593, 563, 907, 941, 947, 953, 991, 977, 983, 607, 641, 647, 653, 677, 683, 661, 1091, 1093, 1061, 1063, 1193, 1163, 1597, 1567, 1901, 1907, 1913, 1993, 1997, 1601, 1607, 1613, 1663, 1667, 2297, 2267

Offset

1,1

Comments

Terms ordered according to first prime found but shown after flipping its 6's and 9's. - Harvey P. Dale, Feb 07 2015

The first term that contains both 6's and 9's is 2963. - Harvey P. Dale, Feb 07 2015

Links

Table of n, a(n) for n=1..48.

Example

991 is prime, flipping the 9's we get 661 which is also prime.

Mathematica

fd96Q[n_]:=Module[{idn=IntegerDigits[n]}, (MemberQ[idn, 6]||MemberQ[idn, 9]) &&PrimeQ[FromDigits[idn/.{6->9, 9->6}]]]; FromDigits[IntegerDigits[#]/.{6->9, 9->6}]&/@Select[Prime[Range[400]], fd96Q] (* Harvey P. Dale, Feb 07 2015 *)

Prog

(PARI) flip69pr(n) = { for(x=1, n, y=x; v=0; v1=0; f=0; ln =length(Str(x)); a = vector(ln); b = vector(ln); forstep(j=ln, 1, -1, r = y%10; a[j]=r; b[j]=r; if(r==6, a[j] = 9; f=1); if(r==9, a[j] = 6; f=1); y = floor(y/10); ); forstep(j=ln, 1, -1, v=v+a[j]*10^(ln-j); v1=v1+b[j]*10^(ln-j); ); if(isprime(v) && isprime(v1) && f, print1(v", ")); ) }

Crossrefs

Sequence in context: A068830 A033417 A182690 * A244192 A075478 A126146

Adjacent sequences: A088863 A088864 A088865 * A088867 A088868 A088869

Keyword

nonn,base

Author

Cino Hilliard, Nov 26 2003

Status

approved