A132785 - OEIS

%I #5 May 12 2014 00:19:53

%S 1,1,1,1,2,7,40,342,4118,66581,1393998,36722251,1189340060,

%T 46466456210,2155486553918,117137645018204,7372271485024724,

%U 532031521606758006,43644205623323138712,4038679603699275061593,418716209086799704826908

%N Main diagonal of triangle A132784.

%C Also equals (with offset) the row sums and rightmost border of triangle A132784.

%o (PARI) {a(n)=local(A=[1]);if(n==0,1, for(i=1,n,B=Vec(Pol(A)/(1-x +x*O(x^(i*(i-1)/2))));A=concat(vector(i),B));A[n+1])}

%Y Cf. A132784 (triangle), A132786 (column sums).

%K nonn

%O 0,5

%A _Paul D. Hanna_, Aug 29 2007