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

1,1

Comments

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

Links

Table of n, a(n) for n=1..47.

Formula

Intersection of A305231 and A000037.

Example

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

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

Crossrefs

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

Cf. A325148 (squares).

Sequence in context: A305131 A217073 A210376 * A060317 A033583 A131037

Adjacent sequences: A359978 A359979 A359980 * A359982 A359983 A359984

Keyword

nonn,base

Author

Stefano Spezia, Jan 20 2023

Status

approved