A061337 Smallest number of distinct triangular numbers which sum to n (or -1 if not possible).

0, 1, -1, 1, 2, -1, 1, 2, -1, 2, 1, 2, -1, 2, 3, 1, 2, 3, 2, 3, 4, 1, 2, -1, 2, 2, 3, 2, 1, 2, 3, 2, 3, -1, 2, 3, 1, 2, 2, 2, 3, 3, 2, 2, 3, 1, 2, 3, 2, 2, 3, 2, 3, 3, 3, 1, 2, 2, 2, 3, 2, 2, 3, 3, 2, 2, 1, 2, 3, 2, 2, 3, 2, 2, 3, 3, 2, 3, 1, 2, 3, 2, 3, 2, 2, 3, 3, 2, 2, 3, 3, 1, 2, 2, 2, 3, 3, 2, 3, 2, 2, 2, 2, 3, 3, 1, 2, 3, 2, 3, 3, 2, 2, 3, 2, 2, 3, 3, 3, 2, 1, 2, 3

Offset: 0

Author

Henry Bottomley, Apr 25 2001

Keywords

• sign

Comments

20 is the only case where n>3.

Examples

			a(20)=4 since 20=1+3+6+10, a(21)=1 since 21 is triangular, a(22)=2 since 22=1+21, a(23)=-1 since no combination of distinct triangular numbers sum to 23.
		

Crossrefs

Cf. A000217, A002243, A053614, A061208, A061336.