cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A320561 Irregular table read by rows: T(n,k) = (2*k+1)^(2*k+1) mod 2^n, 0 <= k <= 2^(n-1) - 1.

Original entry on oeis.org

1, 1, 3, 1, 3, 5, 7, 1, 11, 5, 7, 9, 3, 13, 15, 1, 27, 21, 23, 9, 19, 29, 15, 17, 11, 5, 7, 25, 3, 13, 31, 1, 27, 53, 55, 9, 19, 61, 47, 17, 11, 5, 39, 25, 3, 13, 31, 33, 59, 21, 23, 41, 51, 29, 15, 49, 43, 37, 7, 57, 35, 45, 63
Offset: 1

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Author

Jianing Song, Oct 15 2018

Keywords

Comments

The sequence {k^k mod 2^n} has period 2^n. The n-th row contains 2^(n-1) numbers, and is a permutation of the odd numbers below 2^n.
Note that the first 5 rows are the same as those in A320562, but after that they differ.
For all n, k we have v(T(n,k)-1, 2) = v(k, 2) + 1 and v(T(n,k)+1, 2) = v(k+1, 2) + 1, where v(k, 2) = A007814(k) is the 2-adic valuation of k. [Revised by Jianing Song, Nov 24 2018]
For n >= 3, T(n,k) = 2*k + 1 iff k is divisible by 2^floor((n-1)/2) or k = 2^(n-2) - 1 or k = 2^(n-1) - 1.
T(n,k) is the multiplicative inverse of A321901(n,k) modulo 2^n. - Jianing Song, Nov 24 2018

Examples

			Table starts
1,
1, 3,
1, 3, 5, 7,
1, 11, 5, 7, 9, 3, 13, 15,
1, 27, 21, 23, 9, 19, 29, 15, 17, 11, 5, 7, 25, 3, 13, 31,
1, 27, 53, 55, 9, 19, 61, 47, 17, 11, 5, 39, 25, 3, 13, 31, 33, 59, 21, 23, 41, 51, 29, 15, 49, 43, 37, 7, 57, 35, 45, 63,
...
		

Crossrefs

Cf. A007814.
{x^x} and its inverse: this sequence & A320562.
{x^(-x)} and its inverse: A321901 & A321904.
{x^(1/x)} and its inverse: A321902 & A321905.
{x^(-1/x)} and its inverse: A321903 & A321906.

Programs

  • GAP
    T:= Flat(List([1..6],n->List([0..2^(n-1)-1],k->PowerMod(2*k+1,2*k+1,2^n)))); # Muniru A Asiru, Oct 23 2018
  • Mathematica
    Table[PowerMod[(2 k + 1), (2 k + 1), 2^n], {n, 6}, {k, 0, 2^(n - 1) - 1}] // Flatten (* Michael De Vlieger, Oct 22 2018 *)
  • PARI
    T(n,k) = lift(Mod(2*k+1, 2^n)^(2*k+1))
    tabf(nn) = for(n=1, nn, for(k=0, 2^(n-1)-1, print1(T(n, k), ", ")); print);
    

Formula

T(n,k) = A320602(2^n, 2*k+1).
T(n,k) = 2^n - A321901(n,2^(n-1)-1-k). - Jianing Song, Nov 24 2018
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