OFFSET
1,1
FORMULA
{n: A025443(n) = 1}. - R. J. Mathar, Jun 15 2018
MATHEMATICA
With[{nn=60}, Take[Union[Transpose[Select[Tally[Total/@Subsets[Range[nn]^2, {4}]], #[[2]]==1&]][[1]]], nn]] (* Harvey P. Dale, Mar 10 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved