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a(-1) = 4, a(0) = 5; thereafter a(n) = 4 + (Product_{k=1..n} prime(k))^2.
1

%I #7 Dec 04 2017 21:04:17

%S 4,5,8,40,904,44104,5336104,901800904,260620460104,94083986096104,

%T 49770428644836904,41856930490307832904,40224510201185827416904,

%U 55067354465423397733736104,92568222856376731590410384104

%N a(-1) = 4, a(0) = 5; thereafter a(n) = 4 + (Product_{k=1..n} prime(k))^2.

%D M. Aigner and G. M. Ziegler, Proofs from The Book, Springer-Verlag, Berlin, 1999; see p. 21.

%H Harvey P. Dale, <a href="/A055497/b055497.txt">Table of n, a(n) for n = -1..195</a>

%e a(1) = 4 + 2^2 = 8, a(2) = 4 + (2*3)^2 = 40.

%t Join[{4,5},Table[4+Product[Prime[k],{k,n}]^2,{n,15}]] (* _Harvey P. Dale_, Dec 04 2017 *)

%K nonn

%O -1,1

%A _N. J. A. Sloane_, Jul 07 2000 Definition and offset changed by _N. J. A. Sloane_, Dec 04 2017