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.

A355663 Square array A(n, k), n, k >= 0, read by antidiagonals; for any number n with runs in binary expansion (r_w, ..., r_0), let p(n) be the polynomial of a single indeterminate x where the coefficient of x^e is r_e for e = 0..w and otherwise 0, and let q be the inverse of p; A(n, k) = q(p(n) + p(k)).

Original entry on oeis.org

0, 1, 1, 2, 3, 2, 3, 4, 4, 3, 4, 7, 12, 7, 4, 5, 8, 8, 8, 8, 5, 6, 11, 24, 15, 24, 11, 6, 7, 12, 19, 16, 16, 19, 12, 7, 8, 15, 28, 23, 48, 23, 28, 15, 8, 9, 16, 16, 24, 39, 39, 24, 16, 16, 9, 10, 19, 48, 31, 56, 51, 56, 31, 48, 19, 10, 11, 20, 35, 32, 32, 35, 35, 32, 32, 35, 20, 11
Offset: 0

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Author

Rémy Sigrist, Jul 13 2022

Keywords

Comments

In other words, A(n, k) encodes the sum of the polynomials encoded by n and k.

Examples

			Array A(n, k) begins:
  n\k|   0   1   2   3    4    5    6   7    8    9   10   11   12
  ---+------------------------------------------------------------
    0|   0   1   2   3    4    5    6   7    8    9   10   11   12
    1|   1   3   4   7    8   11   12  15   16   19   20   23   24
    2|   2   4  12   8   24   19   28  16   48   35   44   39   56
    3|   3   7   8  15   16   23   24  31   32   39   40   47   48
    4|   4   8  24  16   48   39   56  32   96   71   88   79  112
    5|   5  11  19  23   39   51   35  47   79   99   76  103   71
    6|   6  12  28  24   56   35   60  48  112   67   92   71  120
    7|   7  15  16  31   32   47   48  63   64   79   80   95   96
    8|   8  16  48  32   96   79  112  64  192  143  176  159  224
    9|   9  19  35  39   71   99   67  79  143  195  156  199  135
   10|  10  20  44  40   88   76   92  80  176  156  204  152  184
   11|  11  23  39  47   79  103   71  95  159  199  152  207  143
   12|  12  24  56  48  112   71  120  96  224  135  184  143  240
		

Crossrefs

Programs

  • PARI
    toruns(n) = { my (r=[]); while (n, my (v=valuation(n+n%2, 2)); n\=2^v; r=concat(v, r)); r }
    fromruns(r) = { my (v=0); for (k=1, #r, v=(v+k%2)*2^r[k]-k%2); v }
    A(n,k) = { fromruns(Vec(Pol(toruns(n)) + Pol(toruns(k)))) }

Formula

A(n, k) = A(k, n).
A(n, 0) = n.
A(n, 1) = A014601(n) for any n > 0.
A(n, n) = A001196(n).