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a(n) = Product_{k=1..n} P(k), where P(k) is the smallest prime >= k.
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%I #16 Aug 20 2019 04:25:31

%S 2,4,12,60,300,2100,14700,161700,1778700,19565700,215222700,

%T 2797895100,36372636300,618334817100,10511691890700,178698762141900,

%U 3037878956412300,57719700171833700,1096674303264840300,25223508975091326900,580140706427100518700,13343236247823311930100

%N a(n) = Product_{k=1..n} P(k), where P(k) is the smallest prime >= k.

%H Michael De Vlieger, <a href="/A118456/b118456.txt">Table of n, a(n) for n = 1..448</a>

%e a(5)=300 because the smallest primes that are not smaller than 1,2,3,4 and 5 are 2,2,3,5 and 5, respectively, having product 2*2*3*5*5=300.

%p a:=n->product(nextprime(k-1),k=1..n): seq(a(n),n=1..22); # _Emeric Deutsch_, Apr 29 2006

%t FoldList[Times, Table[NextPrime[k - 1], {k, 22}]] (* _Michael De Vlieger_, Aug 21 2017 *)

%o (PARI) a(n) = prod(k=1, n, nextprime(k)); \\ _Michel Marcus_, Aug 20 2019

%Y Cf. A118455, A002110, A034386.

%K easy,nonn

%O 1,1

%A _Leroy Quet_, Apr 28 2006

%E More terms from _Emeric Deutsch_ and _Jonathan Vos Post_, Apr 29 2006