The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A110957 (Sum{k=1..n} 1/c(k))*(product{j=1..n} c(j)), where c(j) is j-th composite. 0

%I

%S 1,10,104,1128,13008,173376,2634624,42422400,722304000,13698201600,

%T 286505164800,6267431116800,143150760345600,3551498315366400,

%U 91568579493888000,2450311107084288000,67966128937598976000

%N (Sum{k=1..n} 1/c(k))*(product{j=1..n} c(j)), where c(j) is j-th composite.

%e Since the first 3 composites are 4, 6 and 8, the third term of the sequence is (1/4 +1/6 +1/8) *4 *6 *8 = 48 +32 +24 = 104.

%p c:=proc(n) if isprime(n)=false then n else fi end: C:=[seq(c(n),n=2..35)]: a:=n->sum(1/C[k],k=1..n)*product(C[j],j=1..n): seq(a(n),n=1..20); # _Emeric Deutsch_, Oct 06 2005

%Y Cf. A002808, A024451.

%K nonn

%O 1,2

%A _Leroy Quet_, Sep 26 2005

%E More terms from _Emeric Deutsch_, Oct 06 2005

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 19 21:32 EDT 2021. Contains 345151 sequences. (Running on oeis4.)