无穷数列\(\{a _{n} \}\)满足：只要\(a _{p} =a _{q} (p , q∈N ^{*} )\)，必有\(a _{p+1} =a _{q+1}\)，则称\(\{a _{n} \}\)为“和谐递进数列”\(.\)若\(\{a _{n} \}\)为“和谐递进数列”，且前四项成等比数列，\(a _{1} =a _{5} =1\)，\(a _{2} =2\)，则\(S _{2021} =\)______．