A088998 Flip 6,9 primes.

19, 29, 59, 97, 79, 89, 61, 67, 109, 139, 149, 191, 193, 199, 197, 179, 163, 167, 229, 239, 293, 263, 269, 349, 359, 397, 379, 389, 367, 409, 419, 439, 449, 491, 499, 479, 461, 463, 467, 509, 593, 599, 563, 569, 907, 911, 919, 929, 937, 941, 947, 953, 991

Offset

1,1

Comments

Surely these are infinite?

Links

Table of n, a(n) for n=1..53.

Formula

For digits d of n if d=6 make it 9 else if d=9 make it 6 and test for prime()

Example

76 -> 79 prime

Prog

(PARI) flip69pr(n) = { for(x=1, n, y=x; v=0; f=0; ln =length(Str(x)); a = vector(ln); forstep(j=ln, 1, -1, r = y%10; a[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) ); if(isprime(v) && f, print1(v", ")); ) }

Crossrefs

Sequence in context: A348561 A287313 A136071 * A181606 A139886 A089724

Adjacent sequences: A088995 A088996 A088997 * A088999 A089000 A089001

Keyword

nonn,base

Author

Cino Hilliard, Nov 02 2003

Status

approved