A321910 - OEIS

%I #42 Dec 06 2018 19:23:46

%S 2,3,5,17,19,23,31,37,41,47,101,103,131,137,139,149,163,167,191,199,

%T 223,227,233,241,251,263,293,311,313,317,331,691,709,719,727,733,787,

%U 823,853,877,887,919,929,937,977,983,997,1013,1019,1021,1031,1049,1129,1171,1367,1399,1409,1511

%N Base-7 deletable primes (written in base 10).

%C A prime p is a base-b deletable prime if when written in base b it has the property that removing some digit leaves either the empty string or another deletable prime.

%C Deleting a digit cannot leave any leading zeros in the new string. For example, deleting the 2 in 2003 to obtain 003 is not allowed.

%H Robert Price, <a href="/A321910/b321910.txt">Table of n, a(n) for n = 1..808</a>

%t b = 7; d = {};

%t p = Select[Range[2, 10000], PrimeQ[#] &];

%t For[i = 1, i <= Length[p], i++,

%t   c = IntegerDigits[p[[i]], b];

%t   If[Length[c] == 1, AppendTo[d, p[[i]]]; Continue[]];

%t   For[j = 1, j <= Length[c], j++,

%t    t = Delete[c, j];

%t    If[t[[1]] == 0, Continue[]];

%t    If[MemberQ[d, FromDigits[t, b]], AppendTo[d, p[[i]]]; Break[]]]];

%t d (* _Robert Price_, Dec 06 2018 *)

%Y Cf. A080608, A080603, A096235-A096246.

%K nonn,base,easy

%O 1,1

%A _Robert Price_, Nov 29 2018