A198146 Primes remaining primes under map 2<=>9 (interchange of decimal digits 2 and 9).

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

Offset: 1

Author

Zak Seidov, Oct 21 2011

Keywords

• nonn
• base

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.

Examples

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

Links

• V. I. Arnold, Experimental observation of mathematical facts (in Russian)

Crossrefs

Cf. A198047 (map 3 <=> 5).

Programs

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]]