A118455 a(1)=1, a(n) = Product_{k=2..n} P(k), where P(k) is the largest prime <= k.

1, 2, 6, 18, 90, 450, 3150, 22050, 154350, 1080450, 11884950, 130734450, 1699547850, 22094122050, 287223586650, 3733906626450, 63476412649650, 1079099015044050, 20502881285836950, 389554744430902050

Offset: 1

Author

Leroy Quet, Apr 28 2006

Keywords

• easy
• nonn

Examples

			a(6)=450 because the largest primes that do not exceed 2,3,4,5 and 6 are, respectively 2,3,3,5 and 5, having product 2*3*3*5*5=450.
		

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..451

Crossrefs

Cf. A118456, A002110, A034386.

Programs

Maple

a:=proc(n) if n=1 then 1 else product(prevprime(k+1),k=2..n) fi end: seq(a(n),n=1..23); # Emeric Deutsch, Apr 30 2006

Mathematica

FoldList[Times, 1, Table[Prime@ PrimePi@ k, {k, 2, 20}]] (* Michael De Vlieger, Aug 21 2017 *)

Extensions

More terms from Emeric Deutsch, Apr 30 2006