3,...,11,15,...,23,...31

3 , ... , 11,15, .... 23, .... 31

A = 3
B = 15-11 = 4

Mencari U2, U5, dan U7 :

U2 :
= a + b
= 3+4=7

U5 :
= a + 4b
= 3+16
= 19

U7 :
= a + 6b
= 3 + 24
= 27

Sehingga ditemukan pola :
= 3,7,11,15,19,23,27,31