A189641 Partial sums of A189640.

0, 0, 1, 1, 1, 2, 3, 3, 4, 4, 4, 5, 5, 5, 6, 7, 7, 8, 9, 9, 10, 10, 10, 11, 12, 12, 13, 13, 13, 14, 14, 14, 15, 16, 16, 17, 17, 17, 18, 18, 18, 19, 20, 20, 21, 22, 22, 23, 23, 23, 24, 25, 25, 26, 27, 27, 28, 28, 28, 29, 30, 30, 31, 31, 31, 32, 32, 32, 33, 34, 34, 35, 36, 36, 37, 37, 37, 38, 39, 39, 40

Offset: 1

Author

Clark Kimberling, Apr 24 2011

Keywords

• nonn

Comments

See A189640.

Crossrefs

Cf. A189640, A189672 (essentially the same).

Programs

Mathematica

(See A189640.)

PARI

a(n) = n--; (n - vecsum(digits(n,3)%2))/2; \\ Kevin Ryde, Apr 23 2021

Formula

a(n) = a(floor((n+2)/3)) + floor(n/3), where a(1)=0.