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

1,3

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

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

Prog

(Scheme, with memoization-macro definec)
(definec (A253887 n) (if (= 2 (modulo n 3)) (A253887 (/ (+ 1 n) 3)) (inv_for_A032766 n)))
(define (inv_for_A032766 n) (+ (* 2 (floor->exact (/ n 3))) (modulo n 3)))
(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

Crossrefs

Odd bisection of A126760.

Cf. A254046 (the corresponding column index).

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

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

Sequence in context: A256946 A285715 A328456 * A026370 A078446 A357241

Adjacent sequences: A253884 A253885 A253886 * A253888 A253889 A253890

Keyword

nonn

Author

Antti Karttunen, Jan 22 2015

Status

approved