A049008 Greatest possible number of right angles that can occur as interior angles in a planar n-gon.

1, 4, 3, 5, 5, 6, 7, 7, 8, 9, 9, 10, 11, 11, 12, 13, 13, 14, 15, 15, 16, 17, 17, 18, 19, 19, 20, 21, 21, 22, 23, 23, 24, 25, 25, 26, 27, 27, 28, 29, 29, 30, 31, 31, 32, 33, 33, 34, 35, 35, 36, 37, 37, 38, 39, 39, 40, 41, 41, 42, 43, 43, 44, 45, 45, 46, 47, 47, 48, 49, 49, 50

Offset: 3

Author

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

Keywords

• easy
• nonn

Comments

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

Examples

			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

Cf. A004396.

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.