# [seqfan] Re: %F A100638 (?!)

franktaw at netscape.net franktaw at netscape.net
Mon Dec 1 06:35:51 CET 2008

```The "formula" line (beginning "Consider the matrix") is a bit confused,
notationally.  Instead of a(5)=[A_11]^2, it should say something like
a(5)=(A^2)_11 (or better, (A^2)_{1,1}), and similarly for the
remaining terms.  (And the 2 at the end of the line is a typo; it
should be 3.)  In other words, A=[a(1),a(2);a(3),a(4)],
A^2=[a(5),a(6);a(7),a(8)], etc.

At a more basic level, how common is the notation [1,2;3,4] to
represent the matrix:
(1 2)
(3 4)?
PARI uses it, but I don't know whether it's in more general use.

-----Original Message-----
From: zak seidov <zakseidov at yahoo.com>

Dear SeqFans,
smtng's wrong with %F A100638 ...
Anyone may wish to clarify, plz,
thx, zak

%I A100638
%S A100638
1,2,3,4,7,10,15,22,37,54,81,118,199,290,435,634,1069,1558,2337,3406,
%T A100638
5743,8370,12555,18298,30853,44966,67449,98302,165751,241570,362355,
%U A100638
528106,890461,1297782,1946673,2837134,4783807,6972050,10458075
%N A100638 Successive elements of powers of the matrix A=[1,2;3,4].
%F A100638 Consider the matrix A=[1, 2;3, 4]. Then a(1)=[A_11],
a(2)=[A_12],
a(3)=[A_21], a(4)=[A_22],
a(5)=[A_11]^2, a(6)=[A_12]^2, a(7)=[A_21]^2,
a(8)=[A_22]^2,
a(9)=[A_11]^3,
a(10)=[A_12]^2, ...
%Y A100638 Sequence in context: A078159 A129490 A018132 this_sequence
A033320
A013982 A051449
%Y A100638 Adjacent sequences: A100635 A100636 A100637 this_sequence
A100639
A100640 A100641
%K A100638 easy,nonn
%O A100638 1,2
%A A100638 Simone Severini (ss54(AT)york.ac.uk), Dec 04 2004

```