

A202386


Numbers n such that the difference between the square of n and the square of the reversal of n is itself a perfect square.


4



65, 5625, 6565, 50721, 65065, 71555, 75515, 84295, 541063, 557931, 650065, 650606, 656565, 699796, 809325, 827372, 934065, 2855182, 4637061, 4854634, 5791775, 5883141, 5951693, 6129084, 6500065, 6731076, 6752626, 6791774, 7768827, 8084505, 9349065
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

Numbers ending in 0 are excluded.
This sequence is infinite because 65*10^n + 65 is a term for all n > 1.


REFERENCES

A. H. Beiler, Recreations in the Theory of Numbers, Dover, NY, 1996, p. 147.


LINKS

Giovanni Resta, Table of n, a(n) for n = 1..200


EXAMPLE

5625 belongs to this sequence because 5625^2  5265^2 = 1980^2.


MATHEMATICA

lst = {}; Do[a = n^2; b = FromDigits[Reverse[IntegerDigits[n]]]^2; If[MatchQ[Sqrt[a  b], _Integer] && ! a == b, AppendTo[lst, n]], {n, 85000}]; Select[lst, ! Mod[#, 10] == 0 &]


CROSSREFS

Cf. A068536, A000290.
Sequence in context: A110900 A084272 A146756 * A294955 A115432 A116104
Adjacent sequences: A202383 A202384 A202385 * A202387 A202388 A202389


KEYWORD

nonn


AUTHOR

Arkadiusz Wesolowski, Dec 18 2011


STATUS

approved



