A127177 Primes whose "Look And Say" descriptions from right to left (in the sense of method A, i.e., frequency followed by digit-indication) are also primes.

3, 7, 71, 103, 113, 163, 173, 311, 313, 331, 337, 349, 373, 757, 773, 797, 919, 953, 977, 991, 1109, 1123, 1151, 1171, 1181, 1213, 1237, 1277, 1279, 1297, 1327, 1423, 1447, 1543, 1553, 1567, 1621, 1663, 1669, 1747, 1811, 1873, 1877, 1889, 1993, 1999, 3049

Offset: 1

Author

Lekraj Beedassy, Jan 07 2007

Keywords

• nonn
• base

Examples

			71, 331 and 1277, for instance, belong to the sequence because their respective descriptions 1171 (one 1, one 7), 1123 (one 1, two 3's) and 271211 (two 7's, one 2, one 1) are primes.
		

Crossrefs

Cf. A006711, A127178, A127179.

Programs

Mathematica

LookAndSayA[ n_] := FromDigits@Flatten@((Through[ {Length, First}[ # ] ] &) /@ Split@Reverse@IntegerDigits@n); Select[Prime@Range[450],PrimeQ@LookAndSayA@# &] (* Ray Chandler, Jan 16 2007 *)

Extensions

Extended by Ray Chandler, Jan 16 2007