# [seqfan] Re: Fwd: Problems with A072229

Maximilian Hasler maximilian.hasler at gmail.com
Mon Apr 13 23:07:26 CEST 2009

```concerning that sequence,
A072229
Witt index of the standard bilinear form <1,1,1,...,1> over the
0, 0, 0, 0, 1, 2, 3, 4, 4, 4, 4, 5, 6, 7, 8, 8, 8, 8, 9, 10, 11, 12,
12, 12, 12, 13, 14, 15, 16

I agree that the author must have meant
a(n) = 4 floor( n/7 ) + [0,0,0,0,1,2,3][ n % 7 + 1]

But I don't understand the kw "more", given this formula (and the
keyword "easy" ... !)

Maximilian

On Mon, Apr 13, 2009 at 1:49 PM,  <franktaw at netscape.net> wrote:
> There are some problems with your sequence A072229.  You gave the
> formula:
>
> a(n) = n/2 + (0, 0, 0, 0, 1, 2, 3, 4) depending on residue of n mod 8.
>
>
> But if n/2 means floor(n/2), this would make the sequence start:
>
> 0,0,1,1,3,4,6,7
>
> instead of 0,0,0,0,1,2,3,4.  I would guess that what you want is
> actually 4*floor(n/8) + ....
>
> Furthermore, the terms shown do not match this formula: there is one
> less of each multiple of 4 than there should be.  In other words, what
> is actually present is:
>
> 4*floor(n/7) + (0, 0, 0, 0, 1, 2, 3)[n mod 7].
>
> I don't know anything about bilinear forms, so I can't tell if it is
> the formula or the values that is incorrect.
>
>
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>

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