a(n) = Sum_{k=0..n} (-1)^k * binomial(3*n-k+3,n-k).
A390588
a(n) = Sum_{k=0..n} (-1)^k * binomial(3*n-k+3,n-k).
Terms
- a(0) =1a(1) =5a(2) =29a(3) =174a(4) =1068a(5) =6656a(6) =41941a(7) =266492a(8) =1704377a(9) =10957957a(10) =70757132a(11) =458544280a(12) =2980752184a(13) =19427502404a(14) =126912484101a(15) =830740684920
External references
- oeis: A390588