A130522 Diagonal immediately below the main diagonal of triangle A130521.
1, 1, 3, 8, 25, 89, 349, 1496, 6962, 34861, 186678, 1063591, 6418167, 40860485, 273513831, 1919284246, 14080876273, 107750778177, 858195666410, 7100543662976, 60922480229704, 541193416875432, 4970306167860426
Offset: 0
Keywords
Programs
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PARI
{a(n)=if(n<0,0,if(n<=1,1,sum(k=0,n\2+1,(binomial(n-k,k)+binomial(n-k+1,k-1))*a(n-k-1))))}
Formula
a(n) = Sum_{k=0..[n/2]+1} [C(n-k,k) + C(n-k+1,k-1)]*a(n-k-1) for n>=2, with a(0)=a(1)=1.
Comments