Triple factorial numbers a(n) = n!!!, defined by a(n) = n*a(n-3), a(0) = a(1) = 1, a(2) = 2. Sometimes written n!3.

A007661

Triple factorial numbers a(n) = n!!!, defined by a(n) = n*a(n-3), a(0) = a(1) = 1, a(2) = 2. Sometimes written n!3.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =3a(4) =4a(5) =10a(6) =18a(7) =28a(8) =80a(9) =162a(10) =280a(11) =880a(12) =1944a(13) =3640a(14) =12320a(15) =29160a(16) =58240a(17) =209440a(18) =524880a(19) =1106560a(20) =4188800a(21) =11022480a(22) =24344320a(23) =96342400a(24) =264539520a(25) =608608000a(26) =2504902400a(27) =7142567040a(28) =17041024000a(29) =72642169600

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