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

1,1

Links

Table of n, a(n) for n=1..47.

Example

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.

Mathematica

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

Crossrefs

Cf. A006711, A127178, A127179.

Sequence in context: A088797 A165589 A184316 * A261136 A127179 A359748

Adjacent sequences: A127174 A127175 A127176 * A127178 A127179 A127180

Keyword

nonn,base

Author

Lekraj Beedassy, Jan 07 2007

Extensions

Extended by Ray Chandler, Jan 16 2007

Status

approved