Quel est le prochain nombre?

1)  3, 4, 7, 8, 11, 12, ???     (a.7,   b.10,  c.14,  d.15) 2)  31, 29, 24, 22, 17, ???   (a.15,  b.14,  c.13,  d.12) 3)  21, 9, 21, 11, 21, 13,  ???   (a.14,  b.15,  c.21,  d.23) 4)  53, 53, 40, 40, 27, 27,  ???   (a.12,  b.14,  c.27,  d.53) 5)  2, 6, 18, 54, ???   (a.108,  b.148,  c.162,  d.216) 6)  1,000, 200, 40, .???   (a.8,  b.10,  c.15,  d.20) 7)  7, 10, 8, 11, 9, 12, ???   (a.7,  b.10,  c.12,  d.13) 8)  14, 28, 20, 40, 32, 64, ???   (a.52,  b.56,  c.96,  d.128) Voir la réponse