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

1,1

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

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)

Prog

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

Crossrefs

Cf. A026177.

Sequence in context: A349616 A197683 A118737 * A026221 A030740 A325279

Adjacent sequences: A026211 A026212 A026213 * A026215 A026216 A026217

Keyword

nonn

Author

Clark Kimberling

Status

approved