0,1

n=3:

.__.__.__.

|__|__|__|

Names of nodes:

1 2 3 4

a b c d

Maximal directed paths which start from node 3:

34dcba123c

34dc32ba12

34dc321ab2

34dc321abc

3cd432ba12

3cd4321ab2

3cd4321abc

3cba1234dc

321abc34dc

321abcd43c

There are also paths from nodes c,b,2. So n(3)=4*10=40

Cf. A089243.

Sequence in context: A125712 A062290 A078541 this_sequence A143231 A104039 A083546

Adjacent sequences: A135440 A135441 A135442 this_sequence A135444 A135445 A135446

nonn

Yasutoshi Kohmoto zbi74583(AT)boat.zero.ad.jp, Feb 18 2008