0,2

a(n)/4^n tends to zero as n increases.

a(2n)=4*a(2n-1)-A054474(n); a(2n+1)=4*a(2n).

a(2)=12 since there are 16 2-step walks but 4 of them involve a return to the origin at some stage; similarly a(3)=48 since there are 64 3-step walks but 16 of them involve a return to the origin at some stage.

Sequence in context: A032380 A057346 A081620 this_sequence A108508 A019309 A056632

Adjacent sequences: A063884 A063885 A063886 this_sequence A063888 A063889 A063890

nonn

Henry Bottomley (se16(AT)btinternet.com), Aug 28 2001