A336321 a(n) = A122111(A225546(n)).

1, 2, 3, 4, 7, 5, 19, 6, 9, 11, 53, 10, 131, 23, 13, 8, 311, 15, 719, 22, 29, 59, 1619, 14, 49, 137, 21, 46, 3671, 17, 8161, 12, 61, 313, 37, 25, 17863, 727, 139, 26, 38873, 31, 84017, 118, 39, 1621, 180503, 20, 361, 77, 317, 274, 386093, 33, 71, 58, 733, 3673, 821641, 34, 1742537, 8167, 87, 18, 151, 67, 3681131, 626, 1627, 41, 7754077, 35, 16290047

Offset

1,2

Comments

A122111 and A225546 are both self-inverse permutations of the positive integers based on prime factorizations, and they share further common properties. For instance, they map the prime numbers to powers of 2: A122111 maps the k-th prime to 2^k, whereas A225546 maps it to 2^2^(k-1).

In composing these permutations, this sequence maps the squarefree numbers, as listed in A019565, to the prime numbers in increasing order; and the list of powers of 2 to the "normal" numbers (A055932), as listed in A057335.

Links

Michel Marcus, Table of n, a(n) for n = 1..148

Index entries for sequences that are permutations of the natural numbers

Formula

a(n) = A122111(A225546(n)).

Alternative definition: (Start)

Write n = m^2 * A019565(j), where m = A000188(n), j = A248663(n).

a(1) = 1; otherwise for m = 1, a(n) = A000040(j), for m > 1, a(n) = A253550^j(A253560(a(m))).

(End)

a(A000040(m)) = A033844(m-1).

a(A001146(m)) = 2^(m+1).

a(2^n) = A057335(n).

a(n^2) = A253560(a(n)).

For n in A003159, a(2n) = b(a(n)), where b(1) = 2, b(n) = A253550(n), n >= 2.

More generally, a(A334747(n)) = b(a(n)).

a(A003961(n)) = A297002(a(n)).

a(A334866(m)) = A253563(m).

Example

From Peter Munn, Jan 04 2021: (Start)
In this set of examples we consider [a(n)] as a function a(.) with an inverse, a^-1(.).
First, a table showing mapping of the powers of 2:
  n     a^-1(2^n) =    2^n =        a(2^n) =
        A001146(n-1)   A000079(n)   A057335(n)
  0             (1)         1            1
  1               2         2            2
  2               4         4            4
  3              16         8            6
  4             256        16            8
  5           65536        32           12
  6      4294967296        64           18
  ...
Next, a table showing mapping of the squarefree numbers, as listed in A019565 (a lexicographic ordering by prime factors):
  n   a^-1(A019565(n))   A019565(n)      a(A019565(n))   a^2(A019565(n))
      Cf. {A337533}      Cf. {A005117}   = prime(n)      = A033844(n-1)
  0              1               1             (1)               (1)
  1              2               2               2                 2
  2              3               3               3                 3
  3              8               6               5                 7
  4              6               5               7                19
  5             12              10              11                53
  6             18              15              13               131
  7            128              30              17               311
  8              5               7              19               719
  9             24              14              23              1619
  ...
As sets, the above columns are A337533, A005117, A008578, {1} U A033844.
Similarly, we get bijections between sets A000290\{0} -> {1} U A070003; and {1} U A335740 -> A005408 -> A066207.
(End)

Crossrefs

A122111 composed with A225546.

Cf. A336322 (inverse permutation).

Other sequences used in a definition of this sequence: A000040, A000188, A019565, A248663, A253550, A253560.

Sequences used to express relationship between terms of this sequence: A003159, A003961, A297002, A334747.

Cf. A057335.

A mapping between the binary tree sequences A334866 and A253563.

Lists of sets (S_1, S_2, ... S_j) related by the bijection defined by the sequence: (A000290\{0}, {1} U A070003), ({1} U A001146, A000079, A055932), ({1} U A335740, A005408, A066207), (A337533, A005117, A008578, {1} U A033844).

Sequence in context: A167151 A342621 A273014 * A359446 A072275 A122989

Adjacent sequences: A336318 A336319 A336320 * A336322 A336323 A336324

Keyword

nonn

Author

Antti Karttunen and Peter Munn, Jul 17 2020

Status

approved