The pattern follows: multiply by -3 and subtract 3/4. Starting from 1/4: 1/4 x (-3) = -3/4, -3/4 - 3/4 = -3/2 (but the series shows 0). Let me reconsider: 1/4 to 0 is -1/4, 0 to 1 is +1, 1 to -3 is -4, -3 to 13 is +16, 13 to -51 is -64. The multipliers are -4, -4, -4, -4, -4. So -51 x (-4) = 204, then 204 + 1 = 205. Actually, the pattern seems to be: multiply by -4, then add 1. 205 x (-4) + 1 = -820 + 1 = -819.