A060511 Hexagonal excess: smallest amount by which n exceeds a hexagonal number (2k^2-k, A000384).

0, 0, 1, 2, 3, 4, 0, 1, 2, 3, 4, 5, 6, 7, 8, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20

Offset: 0

Author

Henry Bottomley, Mar 22 2001

Keywords

• easy
• nonn

Examples

			a(19)=4 since 15(=2*3^2-3) is the largest hexagonal less than or equal to 19 and 19-15=4.
		

Crossrefs

Cf. A002262, A053186, A055400, A060510.

Programs

Mathematica

Flatten[Range[#]&/@Differences[Array[#(2#-1)&,10,0]]-1] (* Harvey P. Dale, Jun 05 2013 *)