Concatenate Every Second Row for Certain Number of Rows

[PostTIT]

As my title suggests I'm wanting to concatenate data that is in a single column. (e.g. Column A:A)
But I only want to concatenate data in every second row (i.e. A1,A3,A5,etc...)
I have another cell (e.g. B1) that contains an inputted number by the user. I'm looking for this number to limit the amount of cells that are concatenated. (i.e. if "B1 = 6" then I want to concatenate "A1,A3,A5,A7,A9,A11" and if "B1 = 2" then concatenate "A1,A3")

I have tried a simple concatenate function and selected the cells that I want, but I'm looking to automate it using a function (not a macro as I find other users don't appreciate macro-enabled workbooks, therefore don't enable them, therefore miss out on the functions they provide).

I have tried concatenate(transpose) but with the same result as above.

I have tried the following formula:

=CONCATENATE((MOD(ROW(OFFSET($A$1,,,1+2*($B$1-1)))-ROW($A$1),2)=0)*OFFSET($A$1,,,1+2*($B$1-1)))

but it only outputted the final value, not all of them, which wasn't desired.

And then from that I've taken various edits of the OFFSET section of the formula and used with the CONCATENATE and TRANSPOSE functions and had no luck.
I feel like I'm fairly close, but just falling short every time. Any help would be greatly appreciated.

 

[Special-K99]

In a blank sheet put a-h in A1:A8
put 3 in B1

Copying this formula down a column

=IF((MOD(ROW(A1:A1000),2)=1)*(ROW(A1:A1000)<=B$1*2-1),A1:A1000)
Array formula, use Ctrl-Shift-Enter

results in

a
0
c
0
e
0
0
0

I don't have the means to test TEXTJOIN as I'm using an older version of Excel.

 

[wideboydixon]

TEXTJOIN solution is this I think:

Book1
	A	B	C
1	a	8	a,c,e,g,i,k,m,o
2	b
3	c
4	d
5	e
6	f
7	g
8	h
9	i
10	j
11	k
12	l
13	m
14	n
15	o
16	p
17	q
18	r
19	s
20	t
21	u
22	v
23	w
24	x
25	y
26	z
Sheet1

Cell Formulas
Range	Formula
C1	{=TEXTJOIN(",",TRUE,IF(MOD(ROW($A$1:$A$26),2)=1,IF(ROW($A$1:$A$26)<$B$1*2,$A$1:$A$26,""),""))}
Press CTRL+SHIFT+ENTER to enter array formulas.

WBD