387564

Appears in sequences

• Labelings of n diamond-shaped posets with 4 vertices per diamond where the labels follow the poset relations whose associated reading permutation avoids 321 in the classical sense.at n=4A260579
• a(1)=1, a(2)=2; thereafter a(n+1) = Sum_{i=m..n} a(i) where m = (n+1)-k and k is the last digit of a(n), except if k=0, k=1, or k>n then a(n+1) = Sum_{i=1..n} a(i).at n=21A309311