login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A300560 Deep factorization of n, written in binary: replace each factor p^e with the expression [primepi(p) [ e ]], iterate on these numbers, finally replace '[' and ']' with '1' and '0'. 4
0, 1100, 11100100, 11110000, 111100100100, 110011100100, 111110000100, 111110010000, 111001110000, 1100111100100100, 1111100100100100, 1111000011100100, 1110011100100100, 1100111110000100, 11100100111100100100, 111111000000, 1111110000100100, 1100111001110000, 1111110010000100 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Consider the prime factorization of n, replace each factor prime(i)^e_i with the parenthesized expression [i [e_i]], iterate this process on the indices i and exponents e_i, and finally replace '[' and ']' with digits '1' and '0'.

See A300561 for the decimal representation of these binary numbers.

There is redundancy: trailing '0's can be removed without loss of information; then each term ends in a digit 1 which can also be removed. This more condensed version is given in A300562, the decimal representation in A300563(n) = (m/2^valuation(m,2) - 1)/2 with m = a(n) [read in binary] = A300561(n).

The initial a(1) = 0 represents the empty string of binary digits.

LINKS

Table of n, a(n) for n=1..19.

J. Awbrey, https://oeis.org/wiki/Riffs and Rotes, Selected_Sequences, OEIS wiki, Feb. 2010.

EXAMPLE

The first term a(1) = 0 represents, by convention, the empty factorization of the number 1.

2 = prime(1)^1 => (1(1)) => (()) => 1100 = a(2). (The 1's disappear, having empty factorization.)

3 = prime(2)^1 => (2(1)) => ((())()) [using 2 => (())] => 11100100 = a(3).

4 = prime(1)^2 => (1(2)) => (((()))) => 11110000 = a(4).

5 = prime(3)^1 => (3(1)) => (((())())()) => 111100100100 = a(5).

6 = prime(1)^1*prime(2)^1 => (1(1))(2(1)) => (())((())()) => 110011100100 = a(6) (= concatenation of a(2) and a(3), since 6 = 2*3.)

7 = prime(4)^1 => (4(1)) => ((((())))()) => 111110000100 = a(7).

8 = prime(1)^3 => (1(3)) => ((((())()))) => 111110010000 = a(8), and so on.

To convert back to the usual factorization, replace 0 and 1 by ')' and '(', then iteratively replace any (x(y)) by prime_x^y, where an empty x or y means 1.

Examples: 1100 = (()) = (x(y)) with x = y = 1, so (()) = prime_1^1 = 2.

110011100100 = _(())_(_(())_()) = 2 (2()) = 2 prime_2^1 = 6.

111110010000 = (((_(())_()))) = ((_(2())_)) = ((3)) = prime_1^3 = 8.

PROG

(PARI) A300560(n)=(n=factor(n))||return(""); n[, 1]=apply(primepi, n[, 1]); concat(apply(t->Str("1"t[1]"1"t[2]"00"), Col(apply(A300560, n))~))

CROSSREFS

Cf. A300561, A300562, A300563.

Cf. A061396, A062504, A062860.

Sequence in context: A050926 A083933 A080317 * A068279 A278343 A277864

Adjacent sequences:  A300557 A300558 A300559 * A300561 A300562 A300563

KEYWORD

nonn

AUTHOR

M. F. Hasler, Mar 08 2018

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 9 23:09 EDT 2020. Contains 333382 sequences. (Running on oeis4.)