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 A097268 Numbers that are both the sum of two nonzero squares and the difference of two nonzero squares. 23

%I

%S 5,8,13,17,20,25,29,32,37,40,41,45,52,53,61,65,68,72,73,80,85,89,97,

%T 100,101,104,109,113,116,117,125,128,136,137,145,148,149,153,157,160,

%U 164,169,173,180,181,185,193,197,200,205,208,212,221,225,229,232,233

%N Numbers that are both the sum of two nonzero squares and the difference of two nonzero squares.

%C Intersection of A000404 (sum of squares) and A024352 (difference of squares).

%C Also: Numbers of the form x^2+4y^2, where x and y are positive integers. Cf. A154777, A092572, A154778 for analogous sequences. - _M. F. Hasler_, Jan 24 2009

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/SumofSquaresFunction.html">Sum of Squares Function.</a>

%o (PARI) isA097268(n) = forstep( b=2,sqrtint(n-1),2, issquare(n-b^2) && return(1)) \\ _M. F. Hasler_, Jan 24 2009

%Y Cf. A000404, A024352, A097269-A097271.

%K nonn

%O 1,1

%A _Ray Chandler_, Aug 19 2004

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Last modified December 12 14:41 EST 2018. Contains 318075 sequences. (Running on oeis4.)