I did it! More than two years after beginning, I have finally completed my Prime Factorization Cardigan!

Here’s how it works! The stripes each represent a counting number. They go from left to right, cuff to cuff. 1 is black, the background color (which is a factor of everything). Then each prime gets a new color. 2 is blue; 3 is pink; 5 is yellow; 7 is purple….

Composite numbers get the combination of colors for their factors. 6 = 2 x 3, so it’s alternating blue and pink. 10 = 2 x 5, so blue and yellow. 12 = 2 x 2 x 3, so two stitches of blue followed by one of pink….

Perfect powers get multiple rows. 4 = 2 x 2, so two rows of blue; 8 = 2 x 2 x 2, so three rows of blue; 9 = 3 x 3, so two rows of pink. I think my favorite is 36 = 2 x 2 x 3 x 3, so I did two rows of alternating blue and pink.

I put labels in one picture, to give the pattern:

As for details, I used Plymouth Encore yarn, 75% acrylic, 25% wool — it is not expensive and comes in many colors. I looked online for a pattern knitted cuff-to-cuff, and found this Rainbow Lace Jacket. I of course changed the colors. I knitted the stripes in garter stitch, and the rows in between the stripes in black stockinette.

And now for more pictures! First, an overall look at the sweater again:

And with the arms down:

And the back: (I decided to make the numbers go two-dimensionally across the sweater, from cuff to cuff. So the back is a mirror of the front.)

And here’s more detail, Numbers 17 to 32 (The powers of 2 are easy to spot! They are the multiple rows of blue.):

Then Numbers 26 to 38:

34 to 47:

41 to 58:

51 to 63:

And finally, 64 to 78:

There you have it! The latest in my prime factorization knitting adventures. Let’s see, I feel compelled to summarize what I’ve done.

It began with the Prime Factorization Sweater.

Then when that became wildly popular on the internet, I made a Prime Factorization T-shirt. (These are available for sale, by the way.)

I experimented with stripes when I made my Prime Factorization Scarf, and planned out how to do this cardigan.

Then my siblings were expecting babies. For my sister’s baby, I knitted a Coded Blessing Blanket.

For my brother’s baby, nothing but a Prime Factorization Blanket would do.

Which got me going on a Pascal’s Triangle Shawl.

Which got me to start another, prettier one (Still not finished).

And brings me back to the Prime Factorization Cardigan!

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My posts on Mathematical Knitting and related topics are now gathered at Sonderknitting.