A211655 Down-sortable primes: Primes that are also primes after digits are sorted into decreasing order.

2, 3, 5, 7, 11, 13, 17, 31, 37, 41, 43, 53, 61, 71, 73, 79, 83, 97, 113, 131, 149, 157, 163, 167, 179, 181, 191, 197, 199, 211, 241, 251, 281, 311, 313, 331, 337, 347, 359, 373, 389, 419, 421, 431, 433, 443, 461, 463, 491, 521, 541, 563, 571, 593, 613, 617, 631, 641, 643, 653

Offset

1,1

Comments

All 1- and 2-digit reversible primes (A007500) are trivially in this sequence. No primes from A056709 are in this sequence. Clearly all absolute primes (A003459) are sortable primes but not all sortable primes are absolute primes. - Alonso del Arte, Oct 08 2013

Links

Francis J. McDonnell, Table of n, a(n) for n = 1..10000

Francis J. McDonnell, Java Program

Example

131 is prime and after sorting its digits into nonincreasing order we obtain 311, which is prime.
163 is in the sequence because its digits sorted in decreasing order give 631, which is prime. (Note that this is not a reversible prime, since 361 = 19^2.)

Mathematica

Select[Prime[Range[200]], PrimeQ[FromDigits[-Sort[-IntegerDigits[#]]]] &] (* T. D. Noe, Apr 17 2012 *)

Crossrefs

Cf. A004186, A211654, A028864, A028867.

Sequence in context: A105909 A197187 A086498 * A359138 A061461 A359139

Adjacent sequences: A211652 A211653 A211654 * A211656 A211657 A211658

Keyword

nonn,base,easy

Author

Francis J. McDonnell, Apr 17 2012

Status

approved