A365374 - OEIS

%I #47 Dec 11 2023 14:17:25

%S 0,1,2,3,11,19,22,28,33,37,41,72,101,111,121,131,199,202,212,222,232,

%T 288,303,313,323,327,333,377,441,461,732,772,1001,1111,1191,1221,1281,

%U 1331,1371,1411,1721,1919,1999,2002,2112,2192,2222,2282,2332,2372,2412,2722,2828,2888

%N Numbers k such that squaring each digit and concatenating them forms a palindrome.

%C The sequence is infinite since if k is a term then so is 1k1.

%H Michael S. Branicky, <a href="/A365374/b365374.txt">Table of n, a(n) for n = 1..10000</a>

%e k(6) = 19 becomes 181 as 1^2 = 1 and 9^2 = 81;

%e k(7) = 22 becomes  44 as 2^2 = 4 and 2^2 =  4;

%e k(8) = 28 becomes 464 as 2^2 = 4 and 8^2 = 64; etc.

%t Select[Range[0,3000],PalindromeQ@FromDigits@Flatten[IntegerDigits/@(IntegerDigits@#^2)]&]

%o (Python)

%o def ok(n): return (s:="".join(str(int(d)**2) for d in str(n))) == s[::-1]

%o print([k for k in range(3000) if ok(k)]) # _Michael S. Branicky_, Oct 05 2023

%Y Cf. A258373, A366198.

%K base,nonn

%O 1,3

%A _Eric Angelini_ and _Giorgos Kalogeropoulos_, Oct 05 2023