0,4

If the terms (n>0) are written as an array:

1,

1, 2,

1, 2, 3, 3,

1, 2, 3, 3, 4, 5, 4, 5,

1, 2, 3, 3, 4, 5, 4, 5, 5, 7, 7, 8, 5, 7, 7, 8,

1, 2, 3, 3, 4, 5, 4, 5, 5, 7, 7, 8, 5, 7, 7, 8, 6, 9, 10, 11, 9, 12, 11, 13, 6, 9,

then the sum of the m-th row is 3^m (m = 0,1,2,3,...), each column is constant and the terms are from A071585 (a(2^m+k) = A071585(k), k = 0,1,2,...).

If the rows are written in a right-aligned fashion:

1,

1, 2,

1, 2, 3, 3,

1, 2, 3, 3, 4, 5, 4, 5,

1, 2, 3, 3, 4, 5, 4, 5, 5, 7, 7, 8, 5, 7, 7, 8,

..., 7, 7, 8, 5, 7, 7, 8, 6, 9, 10, 11, 9, 12, 11, 13, 6, 9, 10, 11, 9, 12, 11, 13,

then each column is a Fibonacci sequence (a(2^(m+2)+k) = a(2^(m+1)+k) + a(2^m+k), m = 0,1,2,..., k = 0,1,2,...,2^m-1 with a_k(1) = A071766(k) and a_k(2) = A086593(k) being the first two terms of each column sequence). - Yosu Yurramendi, Jun 23 2014

Paul D. Hanna, Table of n, a(n) for n = 0..10000

a(n) = A071585(m), where m = n - floor(log_2(n));

a(0) = 1, a(2^k) = 1, a(2^k + 1) = 2.

a(2^k - 1) = Fibonacci(k+1) = A000045(k+1).

a(2^m+k) = A071585(k), m=0,1,2,..., k=0,1,2,...,2^m-1. - Yosu Yurramendi, Jun 23 2014

a(2^m-k) = F_k(m), k=0,1,2,..., m > log_2(k). F_k(m) is a Fibonacci sequence, where F_k(1) = a(2^(m_0(k))-1-k), F_k(2) = a(2^(m_0(k)+1)-1-k), m_0(k) = ceiling(log_2(k+1))+1 = A070941(k). - Yosu Yurramendi, Jun 23 2014

a(n) = A002487(A059893(A233279(n))) = A002487(1+A059893(A006068(n))), n > 0. - Yosu Yurramendi, Sep 29 2021

a(37) = 5 as it is the denominator of 17/5 = 3 + 1/(2 + 1/2), which is a continued fraction that can be derived from the binary expansion of 4*37 = 2^7 + 2^4 + 2^2; the binary exponents are {7, 4, 2}, thus the differences of these exponents are {3, 2, 2}; giving the continued fraction expansion of 17/5 = [3,2,2].

1, 2, 3, 3/2, 4, 5/2, 4/3, 5/3, 5, 7/2, 7/3, 8/3, 5/4, 7/5, 7/4, 8/5, 6, ...

{1}~Join~Table[Denominator@ FromContinuedFraction@ Append[Abs@ Differences@ #, Last@ #] &@ Log2[NumberExpand[4 n, 2] /. 0 -> Nothing], {n, 120}] (* Version 11, or *)

{1}~Join~Table[Denominator@ FromContinuedFraction@ Append[Abs@ Differences@ #, Last@ #] &@ Log2@ DeleteCases[# Reverse[2^Range[0, Length@ # - 1]] &@ IntegerDigits[4 n, 2], k_ /; k == 0], {n, 120}] (* Michael De Vlieger, Aug 15 2016 *)

(R)

blocklevel <- 6 # arbitrary

a <- 1

for(m in 0:blocklevel) for(k in 0:(2^(m-1)-1)){

a[2^(m+1)+k] <- a[2^m+k]

a[2^(m+1)+2^(m-1)+k] <- a[2^m+2^(m-1)+k]

a[2^(m+1)+2^m+k] <- a[2^(m+1)+k] + a[2^(m+1)+2^(m-1)+k]

a[2^(m+1)+2^m+2^(m-1)+k] <- a[2^(m+1)+2^m+k]

}

a

# Yosu Yurramendi, Jul 11 2014

Cf. A071585, A086593.

Sequence in context: A033803 A035531 A118977 * A007305 A112531 A373553

Adjacent sequences: A071763 A071764 A071765 * A071767 A071768 A071769

easy,nonn,frac

Paul D. Hanna, Jun 04 2002

approved