1,2

A129380(n) = SUM(a(k): 1<=k<n);

a(n) = A129380(n-1)*A000217(n-3) for n>3.

a(n) = SUM(a(k): 1<=k<n)*(n-2)*(n-3)/2 for n>3.

a(5) = (1+2+3)+(1+2+6)+(1+3+6)+(2+3+6) = 6+9+10+11 = 36.

Cf. A083746.

Sequence in context: A082611 A033689 A018324 this_sequence A000308 A018340 A018354

Adjacent sequences: A129376 A129377 A129378 this_sequence A129380 A129381 A129382

nonn

Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 14 2007