A355851 The difference between the indices of the two most recent instances of a(n-1), not including a(n-1) itself, or 0 if not enough such instances exist.

0, 0, 0, 1, 0, 1, 0, 2, 0, 2, 0, 2, 2, 2, 1, 2, 1, 9, 0, 2, 2, 4, 0, 8, 0, 4, 0, 2, 1, 2, 7, 0, 2, 2, 3, 0, 5, 0, 4, 4, 13, 0, 2, 1, 12, 0, 4, 1, 15, 0, 4, 7, 0, 4, 4, 3, 0, 3, 21, 0, 4, 1, 4, 6, 0, 3, 2, 9, 0, 5, 0, 4, 2, 24, 0, 2, 6, 0, 4, 9, 50, 0, 3, 8, 0, 4, 7, 21, 0, 3, 17

Offset: 1

Author

Eric Fox, Jul 19 2022

Keywords

• nonn

Comments

This is similar to Van Eck's sequence: A181391.

Examples

			Say you have 0, 0, 0, 1, 0, 1, 0, 2, 0, 2, 0, 2, 2, ?
The previous term is a 2, and the distance between the pair of most recent 2s before that is 2, hence ? = 2.
		

Crossrefs

Cf. A181391.