OFFSET
1,1
COMMENTS
A025426(a(n)) = 1. - Reinhard Zumkeller, Aug 16 2011
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Square Number
G. Xiao, Two squares
FORMULA
A243148(a(n),2) = 1. - Alois P. Heinz, Feb 25 2019
MATHEMATICA
selQ[n_] := Length[ Select[ PowersRepresentations[n, 2, 2], Times @@ # != 0 &]] == 1; Select[Range[300], selQ] (* Jean-François Alcover, Oct 03 2013 *)
b[n_, i_, k_, t_] := b[n, i, k, t] = If[n == 0, If[t == 0, 1, 0], If[i<1 || t<1, 0, b[n, i - 1, k, t] + If[i^2 > n, 0, b[n - i^2, i, k, t - 1]]]];
T[n_, k_] := b[n, Sqrt[n] // Floor, k, k];
Position[Table[T[n, 2], {n, 0, 300}], 1] - 1 // Flatten (* Jean-François Alcover, Nov 06 2020, after Alois P. Heinz in A243148 *)
PROG
(Haskell)
import Data.List (elemIndices)
a025284 n = a025284_list !! (n-1)
a025284_list = elemIndices 1 a025426_list
-- Reinhard Zumkeller, Aug 16 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved