A254312 -id:A254312 - cp's OEIS frontend

A257480 S(n) = (3 + (3/2)^v(1 + F(4n - 3))(1 + F(4n - 3)))/6, n >= 1, where F(x) = (3x + 1)/2^v(3*x + 1) for x odd, and v(y) denotes the 2-adic valuation of y.

1, 1, 5, 2, 4, 1, 8, 5, 7, 5, 41, 5, 10, 2, 17, 14, 13, 4, 32, 8, 16, 1, 26, 14, 19, 8, 68, 11, 22, 5, 35, 41, 25, 7, 59, 14, 28, 5, 44, 23, 31, 41, 365, 17, 34, 5, 53, 41, 37, 10, 86, 20, 40, 2, 62, 32, 43, 17, 149

Offset: 1

L. Edson Jeffery, Apr 26 2015

nonn

In the following, let F^(k)(x) denote k-fold iteration of F and defined by the recurrence F^(k)(x) = F(F^(k-1)(x)), k > 0, with initial condition F^(0)(x) = x, and let S^(k)(n) denote k-fold iteration of S and defined by the recurrence S^(k)(n) = S(S^(k-1)(n)), k > 0, with initial condition S^(0)(n) = n, where F and S are as defined above.
Theorem 1: For each x, there exists a j>0 such that F^(j)(x) == 1 (mod 4).
Theorem 2: S(n) = m if and only if S(4*n-2) = m.
Conjecture 1: For each n, there exists a k such that S^(k)(n) = 1.
Theorem 3: Conjecture 1 is equivalent to the 3x+1 conjecture.
Theorem 4: The sequence {log(S(n))/log(n)}_{n>1} is bounded with least upper bound equal to log(3)/log(2).
[I have proved Theorems 1--4 (along with several lemmas) and am trying to finish typesetting the draft containing the proofs but had been too ill to finish that work until now. The draft also contains the derivation of the function S from properties of the known function F (A075677). When that paper is completed (hopefully within two weeks) I will then upload it to the links section and delete this comment.]

K. H. Metzger, Untersuchungen zum (3n+1)-Algorithmus, Teil II: Die Konstruktion des Zahlenbaums, PM (Praxis der Mathematik in der Schule) 42, 2000, 27-32.

I. Korec and Štefan Znám, A Note on the 3x+1 Problem, Amer. Math. Monthly 94, 1987, pp. 771-772.
J. C. Lagarias, The 3x + 1 Problem and Its Generalizations, Amer. Math. Monthly 92, 1985, pp. 3-23.
J. C. Lagarias, The 3x+1 Problem: An Annotated Bibliography (1963-2000), arXiv:math/0309224 [math.NT], 2003-2011.
J. C. Lagarias, The 3x+1 Problem: an annotated bibliography, II (2000-2009), arXiv:math/0608208 [math.NT], 2006-2012.

Cf. A006370, A070165, A075677, A256598.
Cf. A241957, A254067, A254311, A257499, A257791 (all used in the proof of Thm 4).
Cf. A253676 (iteration of S terminating at the first occurrence of 1, assuming the 3x+1 conjecture).
Cf. A253720, A254068, A254070, A254131, A254312, A255138, A255168, A258415.

v[x_] := IntegerExponent[x, 2]; f[x_] := (3*x + 1)/2^v[3*x + 1]; s[n_] := (3 + (3/2)^v[1 + f[4*n - 3]]*(1 + f[4*n - 3]))/6; Table[s[n], {n, 59}]

a(n) = my(x=3*n-2, v=valuation(x, 2)); x>>=v; v=valuation(x+1, 2); (((x>>v)+1)*3^(v-1)+1)/2; \\ Ruud H.G. van Tol, Jul 30 2023

A117630 Complement of A056576.

Original entry on oeis.org

2, 5, 8, 10, 13, 16, 18, 21, 24, 27, 29, 32, 35, 37, 40, 43, 46, 48, 51, 54, 56, 59, 62, 65, 67, 70, 73, 75, 78, 81, 83, 86, 89, 92, 94, 97, 100, 102, 105, 108, 111, 113, 116, 119, 121, 124, 127, 130, 132, 135, 138, 140, 143, 146, 149, 151, 154, 157, 159, 162, 165

Offset: 1

Robert G. Wilson v, Apr 08 2006

nonn

A Beatty sequence.

Robert Israel, Table of n, a(n) for n = 1..10000
Index entries for sequences related to Beatty sequences

Cf. A054414, A056576.
Cf. A102525 (decimal expansion of log_3(2)).
Cf. A254312 (sequence arises as exponents in array definition).

[Floor(n*Log(3)/Log(3/2)): n in [1..80]]; // Vincenzo Librandi, Apr 17 2015

seq(floor(n*log[3/2](3)), n=1..100); # Robert Israel, Nov 09 2015

Mathematica
```
Table[Floor[n*Log[3/2, 3]], {n, 61}]
```

vector(100, n, floor(n*log(3)/log(3/2))) \\ Altug Alkan, Nov 10 2015

from operator import sub
from sympy import integer_log
def A117630(n):
    def f(x): return n+sub(*integer_log(1<Chai Wah Wu, Oct 09 2024

a(n) = floor(n*log(3)/log(3/2)).

a(n) = A054414(n) - 1. - Ruud H.G. van Tol, May 10 2024

A254311 Set of all natural numbers m such that m < S(m), where the function S is as defined in A257480.

Original entry on oeis.org

3, 7, 11, 15, 19, 23, 27, 31, 32, 35, 39, 43, 47, 51, 55, 59, 63, 64, 67, 71, 75, 79, 83, 87, 91, 95, 96, 99, 103, 107, 111, 115, 119, 123, 127, 128, 131, 135, 139, 143, 147, 151, 155, 159, 160, 163, 167, 170, 171, 175, 179, 183, 187, 191, 192, 195, 199, 203

Offset: 1

L. Edson Jeffery, May 03 2015

nonn

Theorem: The sequence contains (i) a subset of equivalence class 0 modulo 4 comprising all numbers congruent to 0 modulo 32 and no others; (ii) no numbers congruent to 1 modulo 4; (iii) a subset of numbers congruent to 2 modulo 4; (iv) all numbers of congruence class 3 modulo 4.

Conjecture: A254312 is a permutation of this sequence.

Cf. A254312, A257480.

max = 203; a = {}; v[x_] := IntegerExponent[x, 2]; f[x_] := (3*x + 1)/2^v[3*x + 1]; s[m_] := (3 + (3/2)^v[1 + f[4*m - 3]]*(1 + f[4*m - 3]))/6; Do[If[m < s[m], AppendTo[a, m]], {m, max}]; a

cp's OEIS Frontend

A257480 S(n) = (3 + (3/2)^v(1 + F(4n - 3))(1 + F(4n - 3)))/6, n >= 1, where F(x) = (3x + 1)/2^v(3*x + 1) for x odd, and v(y) denotes the 2-adic valuation of y.

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A117630 Complement of A056576.

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A254311 Set of all natural numbers m such that m < S(m), where the function S is as defined in A257480.

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cp's OEIS Frontend

A257480 S(n) = (3 + (3/2)^v(1 + F(4*n - 3))*(1 + F(4*n - 3)))/6, n >= 1, where F(x) = (3*x + 1)/2^v(3*x + 1) for x odd, and v(y) denotes the 2-adic valuation of y.

Views

Author

Keywords

Comments

References

Links

Crossrefs

Programs

Mathematica

PARI

A117630 Complement of A056576.

Views

Author

Keywords

Comments

Links

Crossrefs

Programs

Magma

Maple

Mathematica

PARI

Python

Formula

A254311 Set of all natural numbers m such that m < S(m), where the function S is as defined in A257480.

Views

Author

Keywords

Comments

Crossrefs

Programs

Mathematica

A257480 S(n) = (3 + (3/2)^v(1 + F(4n - 3))(1 + F(4n - 3)))/6, n >= 1, where F(x) = (3x + 1)/2^v(3*x + 1) for x odd, and v(y) denotes the 2-adic valuation of y.