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up vote 6 down vote favorite 1 If $a_n$ satisfies the linear recurrence relation $a_n = sum_{i=1}^k c_i a_{n-i}$ for some constants $c_i$ , then is there an easy way to find a linear recurrence relation for $b_n = a_n^2$ ? For example, if $a_n = a_{n-1} + a_{n-3}$ , then $b_n=a_n^2$ seems to satisfy $b_n=b_{n-1}+b_{n-2}+3b_{n-3}+b_{n-4}-b_{n-5}-b_{n-6}$ . co.combinatorics share | cite | improve this question asked Nov 28 at 3:56 Erich Friedman 31 1 New contributor Erich Friedman is a new contr