A046712 From the Bruck-Ryser theorem: n == 1 or 2 (mod 4) which are not the sum of 2 squares.

6, 14, 21, 22, 30, 33, 38, 42, 46, 54, 57, 62, 66, 69, 70, 77, 78, 86, 93, 94, 102, 105, 110, 114, 118, 126, 129, 133, 134, 138, 141, 142, 150, 154, 158, 161, 165, 166, 174, 177, 182, 186, 189, 190, 198, 201, 206, 209, 210, 213, 214, 217, 222, 230, 237, 238

Offset

1,1

Comments

Intersection of A022544 and A046712. - Reinhard Zumkeller, Aug 16 2011

References

M. Hall, Jr., Combinatorial Theory, Wiley, New York, 1986, see Theorem 12.3.2.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

R. H. Bruck and H. J. Ryser, The nonexistence of certain projective planes, Canad. J. Math., 1 (1949), 88-93.

Eric Weisstein's World of Mathematics, Bruck-Ryser-Chowla Theorem.

Wikipedia, Bruck-Ryser-Chowla theorem.

Index entries for sequences related to sums of squares

Mathematica

Select[Range[240], (Mod[#, 4] == 1 || Mod[#, 4] == 2) && PowersRepresentations[#, 2, 2] == {} & ] (* Jean-François Alcover, Aug 30 2011 *)
Select[Range[250], MemberQ[{1, 2}, Mod[#, 4]]&&SquaresR[2, #]==0&] (* Harvey P. Dale, Apr 01 2015 *)

Prog

(Haskell)
a046712 n = a046712_list !! (n-1)
a046712_list = filter ((`elem` [1, 2]) . (`mod` 4)) a022544_list
-- Reinhard Zumkeller, Aug 16 2011

Crossrefs

Sequence in context: A064709 A371396 A118129 * A162823 A020171 A122784

Adjacent sequences: A046709 A046710 A046711 * A046713 A046714 A046715

Keyword

nonn,easy,nice

Author

N. J. A. Sloane

Extensions

More terms from James A. Sellers

Status

approved