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Nonsquares which can be expressed as the product of a number and its digit reversal.
1

%I #13 Jan 28 2023 12:02:11

%S 10,40,90,160,250,252,360,403,490,574,640,736,765,810,976,1000,1008,

%T 1207,1210,1300,1458,1462,1612,1729,1855,1944,2268,2296,2430,2520,

%U 2668,2701,2944,3154,3478,3627,3640,4000,4030,4032,4275,4606,4840,4930,5092,5605,5740

%N Nonsquares which can be expressed as the product of a number and its digit reversal.

%C It contains all the numbers of the form i^2*10^(2*j+1).

%F Intersection of A305231 and A000037.

%e 4840 = 220*22 = 22^2*10; 4930 = 58*85; 5092 = 67*76; 5605 = 59*95; 5740 = 140*41.

%t a={}; h=-1; For[k=0, k<=5750, k++, For[m=1, m<=DivisorSigma[0,k], m++, d=Divisors[k]; If[k/Part[d,m] == FromDigits[Reverse[IntegerDigits[Part[d,m]]]] && k>h && !IntegerQ[Sqrt[k]], AppendTo[a, k]; h=k]]]; a

%Y Cf. A000005, A000037, A000290, A004086, A027750, A305231 (supersequence).

%Y Cf. A325148 (squares).

%K nonn,base

%O 1,1

%A _Stefano Spezia_, Jan 20 2023