# [seqfan] Re: Twindragon & other nonconventional bases.

Kevin Ryde user42_kevin at yahoo.com.au
Mon Sep 12 01:57:26 CEST 2016

```antti.karttunen at gmail.com (Antti Karttunen) writes:
>
> I mean that it is almost futile to search with keywords like base i-1
> entered into the OEIS search field.  (Please try it: 4856 results found.)  So
> at least the (normally invisible) anchor-part of the index-entry should be
> something searchable.  Maybe #twindragon would work perfectly well there?

Oh I think I only searched numbers and grepped the names file.  Dunno
what words could most help.  Maybe "complex base" to start, but within
it many possible bases and digits.  Searching that is a bit sparse now
but includes some of some more existing sequences,

A193239    reverse-add steps to palindrome N
A193240    reverse-add trajectory of binary 110
A193241    reverse-add trajectory of binary 10110
A193306    reverse-subtract steps to 0 (plain-rev)
A193307    reverse-subtract steps to 0 (rev-plain)

A256441    N on negative X axis
A271472    N on X axis, in binary

Did anyone answer on Gaussian primes?  With some gp I make (medium
confidence, and not noticing much pattern),

2, 5, 6, 9, 11, 13, 14, 15, 17, 19, 21, 23, 25, 27, 31, 33, 37, 39,
41, 43, 49, 51, 53, 57, 58, 59, 63, 69, 71, 73, 77, 81, 83, 89, 97,
99, 101, 111, 113, 117, 119, 123, 127, 129, 131, 133, 137, 139, 141

or increments

3, 1, 3, 2, 2, 1, 1, 2, 2, 2, 2, 2, 2, 4, 2, 4, 2, 2, 2, 6, 2, 2, 4,
1, 1, 4, 6, 2, 2, 4, 4, 2, 6, 8, 2, 2, 10, 2, 4, 2, 4, 4, 2, 2, 2, 4,
2, 2

or binary

10, 101, 110, 1001, 1011, 1101, 1110, 1111, 10001, 10011, 10101,
10111, 11001, 11011, 11111, 100001, 100101, 100111, 101001, 101011,
110001, 110011, 110101, 111001, 111010, 111011, 111111, 1000101,
1000111, 1001001, 1001101, 1010001, 1010011, 1011001, 1100001,
1100011, 1100101, 1101111, 1110001, 1110101, 1110111, 1111011,
1111111, 10000001, 10000011, 10000101, 10001001, 10001011, 10001101

An even n is even z (x+i*y with x+y even), so the only evens are n = 2,
6, 14, 58 which are z = +/- 1 +/- i.
```