A253887 Row index of n in A191450: a(3n) = 2n, a(3n+1) = 2n+1, a(3n+2) = a(n+1).

1, 1, 2, 3, 1, 4, 5, 2, 6, 7, 3, 8, 9, 1, 10, 11, 4, 12, 13, 5, 14, 15, 2, 16, 17, 6, 18, 19, 7, 20, 21, 3, 22, 23, 8, 24, 25, 9, 26, 27, 1, 28, 29, 10, 30, 31, 11, 32, 33, 4, 34, 35, 12, 36, 37, 13, 38, 39, 5, 40, 41, 14, 42, 43, 15, 44, 45, 2, 46, 47, 16, 48, 49, 17, 50, 51, 6, 52, 53, 18, 54, 55, 19, 56, 57, 7

Offset: 1

Author

Antti Karttunen, Jan 22 2015

Keywords

• nonn

Comments

a(n) gives the row index of n in square array A191450, or equally, the column index of n in A254051.

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000

Crossrefs

Odd bisection of A126760.

Cf. A254046 (the corresponding column index).

Cf. A003602, A032766, A064216, A253786, A253893, A249746.

Cf. A191450, A254051, A254047, A254052, A254104.

Programs

Python

def a(n):
    if n%3==0: return 2*n//3
    elif n%3==1: return 2*(n - 1)//3 + 1
    else: return a((n - 2)//3 + 1)
print([a(n) for n in range(1, 101)]) # Indranil Ghosh, Jun 06 2017

Formula

a(3n) = 2n, a(3n+1) = 2n+1, a(3n+2) = a(n+1).

a(n) = A126760(2n-1).

a(n) = A249746(A003602(A064216(n))). - Antti Karttunen, Feb 04 2015