|
%I #16 Aug 22 2021 14:55:56
%S 7,77,707,717,727,737,747,757,767,777,787,797,7007,7117,7227,7337,
%T 7447,7557,7667,7777,7887,7997,70007,70107,70207,70307,70407,70507,
%U 70607,70707,70807,70907,71017,71117,71217,71317,71417,71517,71617,71717,71817,71917
%N Base-10 palindromes that start with 7.
%C Subsequence of A002113 (palindromic numbers). Union of A222727 (palindromic primes starting with a digit 7) and A222728 (palindromic composite numbers starting with a digit 7). - Jaroslav Krizek, Mar 12 2013
%H Jaroslav Krizek, <a href="/A043042/b043042.txt">Table of n, a(n) for n = 1..2222</a>
%t palQ[n_Integer, base_Integer] := Module[{idn = IntegerDigits[n, base]}, idn == Reverse[idn]]; Select[Range[0, 100000], IntegerDigits[#][[1]] == 7 && palQ[#, 10] &] (* _T. D. Noe_, Mar 12 2013 *)
%t Select[Range[72000],First[IntegerDigits[#]]==7&&PalindromeQ[#]&] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Mar 02 2018 *)
%Y Cf. A002113.
%K nonn,base
%O 1,1
%A _Clark Kimberling_
|
