

A050797


Numbers n such that n^2  1 is expressible as the sum of two nonzero squares in exactly one way.


5



3, 9, 17, 19, 33, 35, 73, 145, 161, 163, 195, 243, 393, 483, 513, 721, 723, 1153, 1763, 2177, 2305, 2593, 4803, 5185, 5833, 6273, 6963, 7057, 7395, 8713, 9523, 9603, 10083, 12483, 13923, 14113, 15875, 17425, 17673, 19043, 20737
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OFFSET

1,1


COMMENTS

If the definition were changed from "nonzero squares" to "nonnegative squares", there would be just one additional term, 1.  T. D. Noe, May 27 2008


LINKS

T. D. Noe, Table of n, a(n) for n=1..300
Eric Weisstein, MathWorld: Sum of Squares Function
Index entries for sequences related to sums of squares


EXAMPLE

E.g. 393^2  1 = 28^2 + 392^2 only.


MATHEMATICA

twoSquaresQ[ n_] := (r = Reduce [0 < a <= b && n^2  1 == a^2 + b^2, {a, b}, Integers]; Head[r] === And); Select[ Range[21000], twoSquaresQ] (* JeanFrançois Alcover, Oct 10 2011 *)


CROSSREFS

Cf. A050798, A050795.
Cf. A000161
Sequence in context: A174180 A106676 A050795 * A103967 A032400 A329422
Adjacent sequences: A050794 A050795 A050796 * A050798 A050799 A050800


KEYWORD

nonn,nice


AUTHOR

Patrick De Geest, Sep 15 1999


EXTENSIONS

More terms from James A. Sellers


STATUS

approved



