fibonacci is nice:
f:|+\
5 f\1 1
but i haven't found a similar expression for Pascal's Triangle. this is the best i can get:
q){x+\\x#1}6
1 1 1 1 1 1
1 2 3 4 5 6
1 3 6 10 15 21
1 4 10 20 35 56
1 5 15 35 70 126
1 6 21 56 126 252
1 7 28 84 210 462