%I #36 Mar 22 2021 18:23:42
%S 1,30,9845550,171634285407048750,193419995622362136809061156168750,
%T 14272693289804307141953423466197932293533748208968750
%N Total number of doubly-even self-dual binary codes of length 8n.
%D F. J. MacWilliams and N. J. A. Sloane, The Theory of Error-Correcting Codes, Elsevier-North Holland, 1978, p. 631.
%F a(n) = 2*Product_{i=1..4n-2} (2^i + 1).
%t Join[{1},Table[2*Product[2^i+1,{i,4n-2}],{n,6}]] (* _Harvey P. Dale_, May 08 2013 *)
%t Table[Product[2^i + 1, {i, 0, n/2 - 2}], {n, 8, 40, 8}] (* _Nathan J. Russell_, Mar 04 2016 *)
%o (Python)
%o for n in range(8, 50, 8):
%o product = 1
%o for i in range(n//2 - 1):
%o product *= 2**i + 1
%o print(product, end=", ")
%o # _Nathan J. Russell_, Mar 01 2016
%Y Cf. A003178, A003179, A028362.
%K nonn,easy,nice
%O 0,2
%A _N. J. A. Sloane_
%E There is an error in Eq. (75) of F. J. MacWilliams and N. J. A. Sloane, the lower subscript should be 1 not 0.
%E Formula corrected by _N. J. A. Sloane_, May 07 2013 following a suggestion from _Harvey P. Dale_