\displaystyle T(1)=1
\displaystyle T(2)=3
\displaystyle T(n)=T(n-2)+2n-1=T(n-2)+n+(n-1) dla n >2

\displaystyle T(n)=n+(n-1)+T(n-2)=
\displaystyle n+(n-1)+(n-2)+(n-3)+T(n-4)=
\displaystyle n+(n-1)+(n-2)+(n-3)+\cdots+4+3+2+1=
\displaystyle \frac {n(n+1)} 2