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A097268 Numbers that are both the sum of two nonzero squares and the difference of two nonzero squares. 23
5, 8, 13, 17, 20, 25, 29, 32, 37, 40, 41, 45, 52, 53, 61, 65, 68, 72, 73, 80, 85, 89, 97, 100, 101, 104, 109, 113, 116, 117, 125, 128, 136, 137, 145, 148, 149, 153, 157, 160, 164, 169, 173, 180, 181, 185, 193, 197, 200, 205, 208, 212, 221, 225, 229, 232, 233 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

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

LINKS

Table of n, a(n) for n=1..57.

Eric Weisstein's World of Mathematics, Sum of Squares Function.

PROG

(PARI) isA097268(n) = forstep( b=2, sqrtint(n-1), 2, issquare(n-b^2) && return(1)) \\ M. F. Hasler, Jan 24 2009

CROSSREFS

Cf. A000404, A024352, A097269-A097271.

Sequence in context: A047615 A140488 A058240 * A226696 A285973 A219639

Adjacent sequences:  A097265 A097266 A097267 * A097269 A097270 A097271

KEYWORD

nonn

AUTHOR

Ray Chandler, Aug 19 2004

STATUS

approved

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Last modified January 23 00:58 EST 2018. Contains 298093 sequences.