# quiz

Thu Dec 4 07:11:06 CET 2003

```    Hello, seqfans.
1/4-sigma or 1/4-aliquot sequence is defined as follows.

s(n)=1/4*sigma(a(n-1))

an example of periodic 1/4-sigma sequence : the period = 25
6943520030720  5386209454080  6389772480000  7665533854902  5756592291840
5657834203560  6382469882880  7938550287360  9055131471360   9256155068160
11798498589696  12316979136000  13937317954560  18314063179776
18071888486400  20136798781440  18850467643392  16492422758400
15699547839573  6635615891520  7400619883008  6494644316160  8009835724800
9317732578770  7847237806128

a quiz :
How did I get this example?
1. A good method to calculate exists.
2. Exhaustive search.
3.Others.

1. A problem such that x=1/4*sigma(1/4*sigma....25 times....(x)....) is
too difficult to solve.
2. 14 digits is too many to do an exhaustive search.
3. What is it?

to Neil :
Managing any public project like OEIS is hard thing.

You receive a hundred sequences per day?
You add them on OEIS as a routine work.
Each sequence is "one of many sequences" for you, but an  author of the
sequence never thinks so, it is the "only one sequence" for him.
If you slight them, they  will claim you with many mails.
I did it several times.

But I think that if one really knows the purpose of OEIS then he will
not claim so much.
Explain it again to seqfans.
I suppose that a purpose of OEIS is "identification", but if so, why do
some "foolish" sequences such as  "Kanji-sequence" exist?
It wastes 0.000001 sec for searching   sequences.
If the purpose is "to be a encyclopedia" then people allows the
existence of a category " related with word".
But I feel that some of my sequences which were rejected  fit to  a
"encyclopedia", though they don't fit to   the identification.
For example, above periodic 1/4-sigma sequence which was once rejected.

Yasutoshi

```