The differences are: 3, 5, 7, 9 (increasing by 2 each time). So, 18 + 9 = 27.

B=2, A=1, D=4; sum = 2 + 1 + 4 = 7.

C=3, A=1, B=2, so 'CAB' = 312.

D=4, O=15, G=7; C=3, A=1, T=20. The code for 'CAT' is 3120.

Each letter is shifted by +1: B->C, I->J, R->S, D->E, so 'BIRD' = 'CJSF'.

The pattern skips one letter each time: A (skip B) C (skip D) E (skip F) G, so next is I.

All numbers except 30 are perfect squares.