A1b2c3d4e5f6g7h8i9j10k11l12m13n14o15p16q17r18s19t20u21v22w23x24y25z26 -

with numbers 1 through 26 .

You’ve listed a sequence that pairs each letter of the alphabet with a number: with numbers 1 through 26

This is a common (A1Z26), where each letter is replaced by its position in the alphabet. the piece reads:

If you meant this as a puzzle or code, the piece reads: with numbers 1 through 26