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A088866
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Primes where flipping 6 and 9 is also prime.
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0
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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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| 991 is prime. flipping the 9's we get 661 which is also prime.
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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", ")); ) }
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CROSSREFS
| Sequence in context: A068830 A033417 A182690 * A075478 A126146 A112667
Adjacent sequences: A088863 A088864 A088865 * A088867 A088868 A088869
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KEYWORD
| nonn,base
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AUTHOR
| Cino Hilliard (hillcino368(AT)gmail.com), Nov 26 2003
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