anbn==2an−1+3bn−1+bn−2
For a positive integer n, consider the two recurrence relations above subjected to the conditions a1=0 and b1=b2=1.
If the value of the expression (ab2015+3)(ab2016+3) can be expressed as pbqsr, where bq is one of the terms in the recurrence relations sequence above and (p,r) and (r,s) are pairwise coprime integers.
Find the value of (p+q+r+s)mod673.