OFFSET

3,2

COMMENTS

Reflex angles (e.g. 270 degrees) are not considered right angles. From a(6) on, this duplicates A004396 from its eighth term.

FORMULA

a(3) = 1; a(4) = 4; a(5) = 3; a(3*k+3) = 2*k+3; a(3*k+4) = 2*k+3; a(3*k+5) = 2*k+4 where k starts from 1 OR a(n) is the greatest integer less than 2/3*(n+2) where n starts from 6.

EXAMPLE

a(3) = 1 because you can only have one right angle in a triangle; a(4) = 4 as in a rectangular quadrilateral; a(100) = 67 etc.

CROSSREFS

KEYWORD

easy,nonn

AUTHOR

Deepak R. N (deepak_rama(AT)bigfoot.com)

STATUS

approved