Can anyone explain to me what's lacsap's fraction? Also how to find the general term use to find the numerator and denominator?

This looks suspiciously like Pascal’s Triangle, which is a way of generating and organizing the binomial coefficients. Or see Wolfram Mathworld.

Pascal’s triangle has wide appeal for its rich mathematical properties, a little surprising for its underlying simplicity. There’s a connection to the Fibonacci sequence, which in turn gives rise to the Golden Ratio & rectangle. Binomial coeffecients are central to combinatorics & probability theory as well. Dynamite stuff from a 17C French genius!

So what’s with the backward spelling?

Lacsap is Pascal backwards. Pascal’s fraction triangle (just an image, not a description) is a way to arrange fractions. Starting with1/1 at the top, the numerator (top number) is increased by one each step to downward right, and the denominator (bottom number) is increases by one each step to the downward left. Each fraction on the inside thereby has the numerator of the fraction to its upper-right, and the denominator of the fraction to its upper-left. Every fraction appears on this triangle somewhere.

If you want the xth number in row n the formula is
x/(n + 1 – x)

Find out the formula to find the denominator( his the row number and r is the element: Element is like column) and r=0 in the first element

Lacsap’s fractions

1 1

1 3 1

2

1 6 6 1

4 4

1 10 10 10 1

7 6 7

1 15 15 15 15 1

11 9 9 11