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A097268
Numbers that are both the sum of two nonzero squares and the difference of two nonzero squares.
24
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
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
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
KEYWORD
nonn
AUTHOR
Ray Chandler, Aug 19 2004
STATUS
approved