OFFSET

0,9

COMMENTS

LINKS

R. Zumkeller, Table of n, a(n) for n = 0..10000

FORMULA

a(n) = n/2 + O(sqrt(n)). - Charles R Greathouse IV, Aug 28 2016

EXAMPLE

a(8) = #{6+2, 5+3} = 2;

a(9) = #{7+2, 6+3} = 2;

a(10) = #{8+2, 7+3, 5+5} = 3;

a(11) = #{8+3, 6+5} = 2;

a(12) = #{10+2, 7+5, 6+6} = 3;

a(13) = #{11+2, 10+3, 8+5, 7+6} = 4.

PROG

(PARI) a(n)=n\2 - sqrtint(n) + sum(k=sqrtint(n\2)+1, sqrtint(n), issquare(n-k^2)) \\ Charles R Greathouse IV, Aug 28 2016

CROSSREFS

KEYWORD

nonn,easy

AUTHOR

Reinhard Zumkeller, Jan 26 2010

EXTENSIONS

Typo in b-file link fixed by Reinhard Zumkeller, Feb 10 2010

STATUS

approved