Descopara regula si continua sirul cu anca patru numere:
a) 393,396,399,....,....,....,......;
b) 681,677,673,....,....,.....,.....;
c) 123,321,234,432,.....,.....,.....,......;
d) 207,217,227,......,.....,.....,.....;
e) 132,234,336,........,......,......,......;