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A028570 Numbers k such that k*(k + 9) is a palindrome.

%I A028570 #27 Sep 08 2022 08:44:50
%S A028570 0,2,12,44,137,157,167,248,258,1639,1664,1694,5392,15904,16997,160187,
%T A028570 487619,1547147,14674184,14790532,15019614,15336644,25234083,26132578,
%U A028570 26211438,26216753,48675319,49407017,52030352,54072524,151698472,164399727,497665874
%N A028570 Numbers k such that k*(k + 9) is a palindrome.
%H A028570 Michael S. Branicky, <a href="/A028570/b028570.txt">Table of n, a(n) for n = 1..42</a>
%H A028570 Patrick De Geest, <a href="http://www.worldofnumbers.com/consemor.htm">Palindromic Quasipronics of the form n(n+x)</a>
%H A028570 Erich Friedman, <a href="https://erich-friedman.github.io/numbers.html">What's Special About This Number?</a> (See entries 258, 1664.)
%t A028570 Select[Range[0, 9999], PalindromeQ[#^2 + 9#] &] (* _Alonso del Arte_, Nov 10 2019 *)
%o A028570 (Scala) def palQ(n: Int, b: Int = 10): Boolean = n - Integer.parseInt(n.toString.reverse) == 0
%o A028570 (0 to 9999).filter((n: Int) => palQ(n * n + 9 * n)) // _Alonso del Arte_, Nov 10 2019
%o A028570 (Magma) f:=func<n| Intseq(n) eq Reverse(Intseq(n))>; [k:k in [0..2*10^7]| f(k*(k+9))]; // _Marius A. Burtea_, Nov 11 2019
%o A028570 (Python)
%o A028570 from itertools import count, islice
%o A028570 def ispal(n): s = str(n); return s == s[::-1]
%o A028570 def agen():
%o A028570     for k in count(0):
%o A028570         if ispal(k*(k+9)):
%o A028570             yield k
%o A028570 print(list(islice(agen(), 18))) # _Michael S. Branicky_, Jan 25 2022
%Y A028570 Cf. A028569, A028571.
%K A028570 nonn,base
%O A028570 1,2
%A A028570 _Patrick De Geest_
%E A028570 a(27) and beyond from _Michael S. Branicky_, Jan 25 2022