12-Team Round Robin, First and Last Weeks Fixed

[hofa29]

Hi there, trying to implement a 12-team round robin where the first and last week have fixed match pairings. The others can be random for all I care. Have poked around for an algo solution and come up empty. Also tried brute-forcing it but I'm losing my mind. If there's anyone who can do this elegantly/efficiently I'd appreciate. 

Conditions: 
Week 1
1-4
2-11
3-12
5-8
6-10
7-9


Week 11
1-2
3-4
5-6
7-8
9-10
11-12

[Ian Wakeling]

Here is a solution that should work for you where the 11 weeks are the rows.  Additionally the columns are balanced having each team once or twice.  Hope that helps.

( 1  4) ( 2 11) ( 3 12) ( 5  8) ( 6 10) ( 7  9)
( 2 12) ( 6  8) ( 3  5) ( 9 11) ( 4  7) ( 1 10)
( 8 10) ( 9 12) ( 2  6) ( 4  5) ( 7 11) ( 1  3)
( 2  8) ( 3  9) ( 1 11) ( 4 10) ( 5 12) ( 6  7)
(10 11) ( 5  7) ( 4 12) ( 1  6) ( 2  3) ( 8  9)
( 3 11) ( 6 12) ( 4  8) ( 7 10) ( 1  9) ( 2  5)
( 5  9) ( 3 10) ( 2  7) ( 1 12) ( 8 11) ( 4  6)
( 1  7) ( 4 11) ( 5 10) ( 2  9) ( 3  6) ( 8 12)
( 7 12) ( 1  5) ( 6 11) ( 3  8) ( 4  9) ( 2 10)
( 6  9) ( 2  4) ( 1  8) ( 3  7) (10 12) ( 5 11)
( 5  6) ( 7  8) ( 9 10) (11 12) ( 1  2) ( 3  4)

[hofa29]

THANK YOU!