[seqfan] Re: Natural angry numbers
John W. Layman
layman at math.vt.edu
Fri Oct 9 18:04:39 CEST 2009
If the requirement is that n must be exactly n terms away from n-1, instead of
at least n away or more than n away, I found:
1,4,2,131,129,3,5,16,14,12,10,8,6,31,29,27,25,23,...
and the next term a(19) seemed to be difficult.
Surprisingly, the sequence seems to be
A057167 <http://www.research.att.com/%7Enjas/sequences/A057167> Term in Recaman's sequence A005132 <http://www.research.att.com/%7Enjas/sequences/A005132> where n appears for first time, or 0 if n never appears.
1, 4, 2, 131, 129, 3, 5, 16, 14, 12, 10, 8, 6, 31, 29, 27, 25, 23, 99734, 7, 9, 11, 13, 15, 17, 64, 62, 60, 58, 56, 54, 52, 50, 48, 46, 44, 42, 40, 38, 111, 22, 20, 18, 28, 30, 32, 222, 220, 218, 216, 214, 212, 210, 208, 206, 204, 202, 200, 198, 196
So it's easy to see why a(19)=99734 was difficult.
The "angry" property is not mentioned in A057167 <http://www.research.att.com/%7Enjas/sequences/A057167>.
John
Eric Angelini wrote:
Imagine that an angry natural number could not stand the
presence of his immediate neighbours -- thus asking them to
get away;
The acceptable "get away" distance would be given by the
said angry Natural himself;
This means that "5", for instance, would not accept to see
"4" and "6" at a shorter distance than 5 integers from him;
Sequence S(1) is one packing of such Natural angry numbers:
S(1) = 1,4,7,2,10,13,16,3,5,.,.,8,.,.,.,6,11,.,.,.14,9,.,.,.,.,.,.,.,12,.,.,.,.,.,.,15
... (continued)
and
franktaw at netscape.net replied:
> If the requirement is that the neighbor must be at least n away,
> instead of more than n away, the first packing method gives A072009.
> The corresponding sequence for the second approach is not in the
> database.
>
> A065186 and A065187 are also kind of similar.
>
> One can also look for the lexically first such sequence that is also a
> self-inverse permutation. If I haven't made any mistakes, for Eric's
> definition this starts:
>
> 1,4,8,2,10,17,25,3,19,5,21,34,13,28
>
> while my variant starts:
>
> 1,4,7,2,9,15,3,17,5,19,30,12,25,39,6
>
> For the rule in A065186 (consecutive integers may not be adjacent),
> this starts:
>
> 1,4,6,2,5,3
>
> and then this pattern repeats with each block 6 larger: a(n+6)=a(n)+6.
>
> None of these is in the database.
>
> Franklin T. Adams-Watters
>
>
More information about the SeqFan
mailing list