hello i have been asked to use sigma notation.

i have a sequence here : 7,25,63,129,231,377,575.

aparantly i can use a sigma notation for this.

this is for a study which i am carrying out. above are sequences for total number of 3d squares for each sequences.

i got a formula of 2d already which is 2n^2-2n+1 and i also got a formula for 3d using the formula an^3+bn^2+cn+d.

but as a further part of the study i have to carry out sigma notation.

i have attached the 2d and 3d pictures. for 2d you will reliase i have black squares please ignore that as that is a sepate part of the study. as the moment i am looking at the total number of squares.

all help apreichated

thank you.