# [seqfan] Re: two dumb questions

Sat Jul 22 04:14:24 CEST 2017

```Hi Peter,

Yes, it looks like your triangle has at least one permutation error in row
six.

http://oeis.org/A054521
http://oeis.org/A215200

Also, the definition of A054521 is more standard and easier to understand
than what you propose for Axxxxxx.

Thanks,

On Fri, Jul 21, 2017 at 8:43 PM, Peter Lawrence <peterl95124 at sbcglobal.net>
wrote:

>
> A051731: characteristic triangle of divisors of n
>
> A000005: = number of divisors of n   =   row sums of A051731
>
> 1.  How is A051731 different from Redheffer matrix A143104,
> which seems to have same FORMULA definition ?
> a(i,j) = 1 if j=1 or j|i; 0 otherwise.
>
>
>
>
>
> Axxxxxx:  characteristic triangle of numbers with gcd( I, j ) = 1
>
> A000010 = number of relative-primes of n   =   row sums of Axxxxxx
>
>
> a(i,j) = 1 if gcd(j,i) = 1; 0 otherwise.
>
>  1:   1,                                               1
>  2:   1, 0,                                            1
>  3:   1, 1, 0,                                         2
>  4:   1, 0, 1, 0,                                      2
>  5:   1, 1, 1, 1, 0,                                   4
>  6:   1, 0, 0, 1, 0, 0,                                2
>  7:   1, 1, 1, 1, 1, 1, 0,                             6
>  8:   1, 0, 1, 0, 1, 0, 1, 0,                          4
>  9:   1, 1, 0, 1, 1, 0, 1, 1, 0,                       6
> 10:   1, 0, 1, 0, 0, 0, 1, 0, 1, 0,                    4
> 11:   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0,                 10
> 12:   1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0,              4
> 13:   1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0,           12
> 14:   1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0,        6
> 15:   1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0,     8
> 16:   1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0,  8
>
>
> 2.    I suspect I computed this triangle incorrectly, because I can’t find
> it in the OEIS  _?_
>
>
>
> Peter Lawrence.
>
> --
> Seqfan Mailing list - http://list.seqfan.eu/
>

```