1.
已知无穷等差数列\(\{ \)
\(a_{n}\)\(\}\)中,首项
\(a\)\({\,\!}_{1}=3\),公差
\(d\)\(=-5\),依次取出序号能被\(4\)除余\(3\)的项组成数列\(\{ \)
\(b_{n}\)\(\}.\)
\((1)\)求\(b\)\({\,\!}_{1}\)和\(b\)\({\,\!}_{2}\);
\((2)\)求\(\{\)\(b_{n}\)\(\}\)的通项公式;
\((3)\{\)\(b_{n}\)\(\}\)中的第\(503\)项是\(\{\)\(a_{n}\)\(\}\)中的第几项?