A359981 Nonsquares which can be expressed as the product of a number and its digit reversal.

10, 40, 90, 160, 250, 252, 360, 403, 490, 574, 640, 736, 765, 810, 976, 1000, 1008, 1207, 1210, 1300, 1458, 1462, 1612, 1729, 1855, 1944, 2268, 2296, 2430, 2520, 2668, 2701, 2944, 3154, 3478, 3627, 3640, 4000, 4030, 4032, 4275, 4606, 4840, 4930, 5092, 5605, 5740

Offset: 1

Author

Stefano Spezia, Jan 20 2023

Keywords

• nonn
• base

Comments

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

Examples

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

Crossrefs

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

Cf. A325148 (squares).

Programs

Mathematica

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

Formula

Intersection of A305231 and A000037.