A215090 a(n) = Sum_{i=0..m} d(i)*3^i, where Sum_{i=0..m} d(i)*4^i is the base-4 representation of n.

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

Offset: 0

Author

Clark Kimberling, Aug 03 2012

Keywords

• nonn
• base
• easy

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..10000 (terms 0..1000 from Clark Kimberling)

Crossrefs

Cf. A023717.

Programs

Julia

function a(n)
    m, r, b = n, 0, 1
    while m > 0
        m, q = divrem(m, 4)
        r += b * q
        b *= 3
    end
r end; [a(n) for n in 0:70] |> println # Peter Luschny, Jan 03 2021

Mathematica

t = Table[FromDigits[RealDigits[n, 4], 3], {n, 0, 100}]

PARI

a(n) = fromdigits(digits(n, 4), 3); \\ Michel Marcus, May 02 2018

Formula

a(n) = 3*a(n/4) if n == 0 (mod 4); otherwise a(n) = a(n-1)+1.