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

1,1

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

Table of n, a(n) for n=1..40.

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

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

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

Sequence in context: A247990 A206103 A251302 * A020404 A180454 A216899

Adjacent sequences: A198143 A198144 A198145 * A198147 A198148 A198149

Keyword

nonn,base

Author

Zak Seidov, Oct 21 2011

Status

approved