A265500 Balance scale sequence.

1, 2, 7, 21, 52, 167, 501, 1503, 4509, 13527, 40581

Offset: 1

Author

Ben Paul Thurston, Dec 09 2015

Keywords

• nonn
• more

Comments

Every natural number up to sum(a[1], a[i]) can be written as adding or subtracting unique entries up to a(i).

Examples

			17 = 21-7+1+2, 18=21-1-2, 19=17+2.
		

Links

• The Ben Paul Thurston Blog, Balance scale series

Formula

a(i+1)= 1+2*sum(a[1], a[i]) (proved).