NEED A FORMULA THAT ADDS EVEN OR ODD ROW NUMBERS

[J Shamp]

I am looking for a formula that will sum even or odd row numbers

 

[Duke Carey]

For even rows:
=SUMPRODUCT(--(MOD(ROW(A1:A20),2)=0),A1:A20)

For odd rows:
=SUMPRODUCT(--(MOD(ROW(A1:A20),2)=1),A1:A20)