A127178 Primes whose "Look And Say" descriptions from right to left (in the sense of method B, i.e., digit-indication followed by frequency) are also primes.

3, 7, 23, 59, 71, 83, 89, 103, 131, 233, 269, 311, 317, 349, 389, 409, 461, 479, 499, 547, 601, 619, 631, 641, 643, 683, 709, 719, 727, 733, 757, 787, 821, 853, 859, 911, 937, 971, 983, 1069, 1093, 1223, 1229, 1231, 1291, 1297, 1327, 1381, 1471, 1489, 1531

Offset

1,1

Links

Table of n, a(n) for n=1..51.

Example

71, 499 and 1223, for instance, belong to the sequence because their respective descriptions 1171 (1 once, 7 once), 9241 (9 twice, 4 once), 312211 (3 once, 2 twice, 1 once) are all primes.

Mathematica

LookAndSayB[ n_] := FromDigits@Flatten@((Through[ {First, Length}[ # ] ] &) /@ Split@Reverse@IntegerDigits@n); Select[Prime@Range[400], PrimeQ@LookAndSayB@# &] (* Ray Chandler, Jan 16 2007 *)

Crossrefs

Cf. A022481, A127177, A127179.

Sequence in context: A231722 A168612 A332866 * A001275 A058757 A278455

Adjacent sequences: A127175 A127176 A127177 * A127179 A127180 A127181

Keyword

nonn,base

Author

Lekraj Beedassy, Jan 07 2007

Extensions

Corrected by Ray Chandler, Jan 16 2007

Status

approved