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.

A348475 a(n) = Product_{k=1..A003056(n)} prime(T(n,k)), where T(n,k) = k-th term in row n of A235791.

Original entry on oeis.org

2, 3, 10, 14, 33, 78, 170, 190, 483, 1218, 2046, 4070, 5330, 8385, 33558, 37842, 47082, 127490, 169510, 269445, 825630, 1250886, 1404858, 1969926, 4270910, 6988190, 13239105, 27506490, 29387490, 61019322, 74958702, 77319606, 191617790, 254235170, 715103895, 1549364190
Offset: 1

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Author

Michael De Vlieger, Oct 19 2021

Keywords

Comments

Prime product compactification of A235791.
All terms are squarefree.

Examples

			Row 3 of A235791 contains {3,1}, thus, a(3) = prime(3)*prime(1) = 5*2 = 10.
Omar E. Pol's diagram of rows of A235791:
.                                    y    row a(n) of A067255*   a(n)
Row                                 _|    --------------------------
1                                 _|1| -> 1                 =      2
2                               _|2 _| -> .1                =      3
3                             _|3  |1| -> 1.1               =     10
4                           _|4   _|1| -> 1..1              =     14
5                         _|5    |2 _| -> .1..1             =     33
6                       _|6     _|2|1| -> 11...1            =     78
7                     _|7      |3  |1| -> 1.1...1           =    170
8                   _|8       _|3 _|1| -> 1.1....1          =    190
9                 _|9        |4  |2 _| -> .1.1....1         =    483
10              _|10        _|4  |2|1| -> 11.1.....1        =   1218
11            _|11         |5   _|2|1| -> 11..1.....1       =   2046
12          _|12          _|5  |3  |1| -> 1.1.1......1      =   4070
13        _|13           |6    |3 _|1| -> 1.1..1......1     =   5330
14      _|14            _|6   _|3|2 _| -> .11..1.......1    =   8385
15    _|15             |7    |4  |2|1| -> 11.1..1.......1   =  33558
16  _|16              _|7    |4  |2|1| -> 11.1..1........1  =  37842
...
* we replace 0 with "." for clarity.
		

Crossrefs

Programs

  • Mathematica
    Table[Times @@ Array[Prime@ Ceiling[(n + 1)/# - (# + 1)/2] &, Floor[(Sqrt[8 n + 1] - 1)/2]], {n, 35}]
    (* Use the b-file to generate k rows of A235791 *)
    With[{k = 120}, MapIndexed[Reverse[PrimePi /@ FactorInteger[#][[All, 1]]] &, Import["https://oeis.org/A348475/b348475.txt", "Data"][[1 ;; k, -1]]]] (* Michael De Vlieger, Oct 21 2021 *)