A114778 Cumulative product of triple factorial A007661.

1, 1, 2, 6, 24, 240, 4320, 120960, 9676800, 1567641600, 438939648000, 386266890240000, 750902834626560000, 2733286318040678400000, 33674087438261157888000000, 981936389699695364014080000000

Offset: 0

Author

Jonathan Vos Post, Feb 18 2006

Keywords

• easy
• nonn

Comments

This is the product analog of what for sums is A114347.

Examples

			a(10) = 1!!! * 2!!! * 3!!! * 4!!! * 5!!! * 6!!! * 7!!! * 8!!! * 9!!! * 10!!!
= 1 * 2 * 3 * 4 * 10 * 18 * 28 * 80 * 162 * 280 = 438939648000 = 2^15 * 3^7 * 5^3 * 7^2.
		

Links

• Eric Weisstein's World of Mathematics, Multifactorial.

Crossrefs

Cf. A006882, A000178, A114347.

Formula

a(n) = Product_{j=0..n} j!!!. a(n) = Product_{j=0..n} A007661(j). a(n) = n!!! * a(n-1) where a(0) = 1, a(1) = 1 and n >= 2. a(n) = n*(n-3)!!! * a(n-1) where a(0) = 1, a(1) = 1, a(2) = 2 and n >= 3.