A107868 Column 0 of triangle A107867; a(n) = C( n*(n-1)/2 + n + 1, n).
1, 2, 6, 35, 330, 4368, 74613, 1560780, 38608020, 1101716330, 35607051480, 1285063345176, 51209646652255, 2232785266876080, 105710363656182600, 5399936810873056584, 295998326072989842600, 17328840976366636057110
Offset: 0
Keywords
Programs
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PARI
a(n)=binomial(n*(n-1)/2+n+1,n)