complete the following series : 1,-1,7,5,21,19,43,41,__

The pattern alternates between subtracting 2 and adding 8: 1-2=-1, -1+8=7, 7-2=5, 5+8=13, 13-2=11, 11+8=19, 19-2=17, 17+8=25. However, looking at the series again, the actual pattern is: subtract 2 from odd positions, then add 6 to the result. The pairs are (1,-1), (7,5), (21,19), (43,41) where each pair is (n, n-2). Between pairs: 1 to 7 (+6), -1 to 5 (+6), 7 to 21 (+14), 5 to 19 (+14), 21 to 43 (+22), 19 to 41 (+22). The increments increase by 8. Next increment should be +30, so 43+30=73, 41+30=71. The missing term is 73.