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%I #5 Nov 01 2022 15:57:02
%S 5,91,9091,9181,9271,9361,9451,9541,9631,9721,9811,900991,901891,
%T 902791,903691,904591,905491,906391,907291,908191,909091,910981,
%U 911881,912781,913681,914581,915481,916381,917281,918181,919081,920971,921871,922771
%N Numbers n such that concatenation of n and its 10's complement is a palindrome.
%e a(3)=9091 because 10^4-9091 = 909 and concatenating produces the palindrome
%e 9091909.
%t Select[Range[923000],PalindromeQ[FromDigits[Join[IntegerDigits[#],IntegerDigits[ 10^IntegerLength[ #]-#]]]]&] (* _Harvey P. Dale_, Nov 01 2022 *)
%K base,nonn
%O 1,1
%A _Jason Earls_, Aug 02 2005