# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a096240 Showing 1-1 of 1 %I A096240 #12 Nov 14 2018 02:07:04 %S A096240 3,7,21,59,184,534,1620,4889,15607,50138,165569,551580,1860565,6345080 %N A096240 Number of n-digit base-7 deletable primes. %C A096240 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. "Digit" means digit in base b. %C A096240 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. %t A096240 b = 7; a = {3}; d = {2, 3, 5}; %t A096240 For[n = 2, n <= 7, n++, %t A096240 p = Select[Range[b^(n - 1), b^n - 1], PrimeQ[#] &]; %t A096240 ct = 0; %t A096240 For[i = 1, i <= Length[p], i++, %t A096240 c = IntegerDigits[p[[i]], b]; %t A096240 For[j = 1, j <= n, j++, %t A096240 t = Delete[c, j]; %t A096240 If[t[[1]] == 0, Continue[]]; %t A096240 If[MemberQ[d, FromDigits[t, b]], AppendTo[d, p[[i]]]; ct++; %t A096240 Break[]]]]; %t A096240 AppendTo[a, ct]]; %t A096240 a (* _Robert Price_, Nov 12 2018 *) %Y A096240 Cf. A080608, A080603, A096235-A096246. %K A096240 nonn,base,more %O A096240 1,1 %A A096240 _Michael Kleber_, Feb 28 2003 %E A096240 9 more terms from _Ryan Propper_, Jul 19 2005 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE