A026214 a(n) = (1/2)*s(n), where s(n) is the n-th even number in A026177.

2, 1, 5, 6, 8, 3, 11, 4, 14, 15, 17, 18, 20, 7, 23, 24, 26, 9, 29, 10, 32, 33, 35, 12, 38, 13, 41, 42, 44, 45, 47, 16, 50, 51, 53, 54, 56, 19, 59, 60, 62, 21, 65, 22, 68, 69, 71, 72, 74, 25, 77, 78, 80, 27, 83, 28, 86, 87, 89, 30, 92, 31, 95

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Comments

The even values in A026177 are A026177(3n) = 2n or 6n, and A026177(3n+2) = 6n+4. The odd values are A026177(3n+1) = 2n+1. So a(2n) = A026177(3n)/2 and a(2n+1) = A026177(3n+2)/2. The latter is always the "small" case in A026177. The former is A026177(3n) big or small according to the lowest non-0 ternary digit of 3n, and consequently the formula below for a(n). - Kevin Ryde, Feb 29 2020

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A026177.

Programs

PARI

a(n) = if(n%2 || (n/3^valuation(n,3))%3==1, ceil(3*n/2), n/2); \\ Kevin Ryde, Feb 29 2020

Formula

From Kevin Ryde, Feb 29 2020: (Start)

a(n) = n/2 if n even and A060236(n)=2, otherwise a(n) = ceiling(3n/2), where A060236(n) is the lowest non-0 ternary digit of n.

a(n) = A026177(ceiling(3n/2))/2.

(End)