

A198146


Primes remaining primes under map 2<=>9 (interchange of decimal digits 2 and 9).


0



2293, 2393, 2591, 2693, 2791, 2903, 2957, 5297, 5927, 7297, 7927, 8293, 8923, 9203, 9257, 9323, 9521, 9623, 9721, 9923, 12491, 12497, 12907, 12911, 12967, 12973, 13291, 13921, 14293, 14923, 17291, 17293, 17921, 17923, 19207, 19211, 19267, 19273, 19421, 19427
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OFFSET

1,1


COMMENTS

Only primes containing at least one "2" and one "9" are considered.
Inspired by history (told by VIA himself) that most often mistakes made by V. I. Arnold were caused by mixing 2's and 9's (and also 3's and 5's) in the lengthy calculations by hand.


LINKS



EXAMPLE

2293, 9923 both primes; 2393, 9323 both primes.


MATHEMATICA

p = 29; Reap[Do[id = IntegerDigits[p]; If[Count[id, 2] > 0 && Count[id, 9] > 0 && PrimeQ[FromDigits[(id /. {2 > a, 9 > 2}) /. {a > 9}]], Sow[p]]; p = NextPrime[p], {10^4}]][[2, 1]]


CROSSREFS



KEYWORD

nonn,base


AUTHOR



STATUS

approved



