OFFSET
1,1
COMMENTS
This sequence is infinite because 65*10^k + 65 is a term for all k > 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
Sheng Jiang and Rui-Chen Chen, Digits reversed Pythagorean triples, International Journal of Mathematical Education in Science and Technology, volume 29, number 5, 1998, pages 689-696, see type acca-DRPT.
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 &]
PROG
(PARI) isok(m) = my(r=fromdigits(Vecrev(digits(m)))); (r != m) && (m % 10) && issquare(m^2 - r^2); \\ Michel Marcus, Feb 27 2020
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Arkadiusz Wesolowski, Dec 18 2011
EXTENSIONS
Name clarified by Michel Marcus, Feb 27 2020
STATUS
approved