A308172 a(0)=1; thereafter a(n) = smallest number missing from A081145 after A081145(n) has been calculated.

1, 2, 3, 3, 3, 5, 5, 5, 6, 6, 6, 9, 9, 9, 10, 10, 10, 11, 11, 11, 13, 13, 13, 15, 15, 15, 17, 17, 17, 18, 18, 18, 19, 19, 19, 22, 22, 22, 23, 23, 24, 24, 24, 26, 26, 26, 29, 29, 29, 30, 30, 30, 31, 31, 31, 32, 32, 32, 35, 35, 35, 36, 36, 36, 38, 38, 38, 39, 39, 39, 40, 40, 43

Offset: 0

Author

N. J. A. Sloane, May 16 2019

Keywords

• nonn

Comments

More than the usual number of terms are shown in order to emphasize the irregularities.

Usually the terms appear in groups of three, but there are many irregularities. To see them, take this sequence, apply the RUNS transform twice, and bisect the result. This produces a very irregular sequence, 12, 10, 1, 46, 2, 2, 3, 2, 5, 6, 7, 10, 9, 13, 25, 5, 24, 1, 42, ... It would be nice to understand this better.

Examples

			n=4: Terms 1 through 4 of A081145 are 1,2,4,7. After A081145(4)=7 has been calculated, the numbers not yet in A081145 are 3,5,6,8,..., so a(4) = 3.
		

Links

• Rémy Sigrist, Table of n, a(n) for n = 0..25000
• Rémy Sigrist, PARI program for A308172

Crossrefs

Cf. A081145.

Programs

PARI

See Links section.