26. 在数列{an}\{a_{n}\}{an}中,已知a1=1a_{1}=1a1=1,an+1−an=sin(n+1)π2a_{n+1}-a_{n}=\sin \frac{(n+1)\pi }{2}an+1−an=sin2(n+1)π,则a2022=a_{2022}=a2022= .