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a(n) = 2^(n-1)*(2^n - 1)*Product_{j=1..n-1} (2^j + 1).
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%I #11 Nov 26 2022 02:43:44

%S 0,1,18,420,16200,1138320,152681760,40012315200,20727639504000,

%T 21349793828563200,43852643645542617600,179883715700853141120000,

%U 1474687052822610564537600000,24170122236238340825650936320000

%N a(n) = 2^(n-1)*(2^n - 1)*Product_{j=1..n-1} (2^j + 1).

%H G. C. Greubel, <a href="/A005477/b005477.txt">Table of n, a(n) for n = 0..75</a>

%F a(n) = 2^(n-2)*(2^n - 1)*QPochhammer(n, -1, 2). - _G. C. Greubel_, Nov 25 2022

%p f := i->2^(i-1)*(2^i-1)*product( '2^j+1','j'=1..i-1);

%t Table[2^(n-1) (2^n-1)Product[2^j+1,{j,n-1}],{n,0,20}] (* _Harvey P. Dale_, Feb 02 2022 *)

%t Table[2^(n-2)*(2^n-1)*QPochhammer[-1,2,n], {n,0,30}] (* _G. C. Greubel_, Nov 25 2022 *)

%o (Magma) [n le 1 select n else 2^(n-1)*(2^n -1)*(&*[2^j+1: j in [1..n-1]]): n in [0..25]]; // _G. C. Greubel_, Nov 25 2022

%o (SageMath)

%o def A005477(n): return 2^(n-2)*(2^n-1)*product(2^j+1 for j in range(n))

%o [A005477(n) for n in range(30)] # _G. C. Greubel_, Nov 25 2022

%K nonn

%O 0,3

%A _N. J. A. Sloane_

%E a(0) prepended by _G. C. Greubel_, Nov 25 2022