A383143 Number of positive integers with a shortest addition-subtraction chain of length n.

1, 1, 2, 3, 5, 9, 16, 28, 49, 88, 156, 280, 499, 904, 1639, 2986, 5442, 9936, 18134

Offset: 0

Author

Jinyuan Wang, Apr 17 2025

Keywords

• nonn
• hard
• more

Examples

			a(6) = 16 because the number of occurrences of 6 in A128998 is 16. These numbers are 19, 21, 22, 23, 25, 26, 27, 28, 30, 31, 33, 34, 36, 40, 48, 64.
		

Links

• Neill Clift, Addition Subtraction Chains.
• Index to sequences related to the complexity of n

Crossrefs

Cf. A003065, A128998, A383002, A383142.

Formula

a(n) >= A003065(n).