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Numbers k such that k^2 + 1 is a palindrome.
5

%I #13 Aug 11 2024 14:41:29

%S 0,1,2,10,25,100,1000,1020,1489,2248,10000,10090,100000,100910,102020,

%T 167491,1000000,1000200,1009090,2744934,10000000,10000900,10090910,

%U 24917195,100000000,100909090,103226660,271867456,1000000000,1000002000,1009090910,1577033471

%N Numbers k such that k^2 + 1 is a palindrome.

%H Giovanni Resta, <a href="/A027719/b027719.txt">Table of n, a(n) for n = 1..48</a>

%H P. De Geest, <a href="https://www.worldofnumbers.com/squadd1.htm">Palindromic incremented squares of the form n^2+1</a>

%t palQ[n_] := Block[{d = IntegerDigits[n]}, d == Reverse[d]]; Select[Range[0, 10^5], palQ[#^2 + 1] &] (* _Giovanni Resta_, Aug 29 2018 *)

%Y Cf. A002522, A027720, A002778, A070253.

%K nonn,base

%O 1,3

%A _Patrick De Geest_

%E More terms from _Giovanni Resta_, Aug 28 2018