OFFSET
1,2
COMMENTS
LINKS
Ray Chandler, Table of n, a(n) for n = 1..10000
Reinhard Zumkeller, Table of initial values
MATHEMATICA
wmax = 1000;
triples[w_] := Reap[Module[{u, v}, For[u = 1, u < w, u++, If[IntegerQ[v = Sqrt[(u^2 + w^2)/2]], Sow[{u^2, v^2, w^2}]]]]][[2]];
tt = Flatten[DeleteCases[triples /@ Range[wmax], {}], 2];
Position[tt, t_List /; SquareFreeQ[GCD@@t]] // Flatten (* Jean-François Alcover, Oct 24 2021 *)
PROG
(Haskell)
import Data.List (elemIndices)
a198409 n = a198409_list !! (n-1)
a198409_list = map (+ 1) $ elemIndices 1 $ map a008966 $
zipWith gcd a198384_list $ zipWith gcd a198385_list a198386_list
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Oct 25 2011
STATUS
approved