OFFSET
1,1
COMMENTS
a(n) = sqrt(A120089).
LINKS
FORMULA
a(n) = 2*u*v, where u=sqrt(j/2) and v=sqrt(j+k) {for coprime pairs(j,k) j>k with odd k such that pairs (u,v) are coprime with v odd}.
MAPLE
isA024364 := proc(an) local r::integer, s::integer ; for r from floor((an/4)^(1/2)) to floor((an/2)^(1/2)) do for s from r-1 to 1 by -2 do if 2*r*(r+s) = an and gcd(r, s) < 2 then RETURN(true) ; fi ; if 2*r*(r+s) < an then break ; fi ; od ; od : RETURN(false) ; end : for n from 2 to 1200 do if isA024364(n^2) then printf("%d, ", n) ; fi ; od ; # R. J. Mathar, Jun 08 2006
MATHEMATICA
isA024364[an_] := Module[{r, s}, For[ r = Floor[(an/4)^(1/2)], r <= Floor[(an/2)^(1/2)], r++, For[s = r - 1, s >= 1, s -= 2, If[2 r (r + s) == an && GCD[r, s] < 2, Return[True]]; If[2 r (r + s) < an, Break[]]]]; Return[False]];
Select[Range[2, 2000], If[isA024364[#^2], Print[#]; True, False]&] (* Jean-François Alcover, May 24 2024, after R. J. Mathar *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Lekraj Beedassy, Jun 07 2006
EXTENSIONS
Corrected and extended by R. J. Mathar, Jun 08 2006
STATUS
approved