OFFSET
1,2
COMMENTS
Also, number of n X n orthogonal matrices over GF(11) with determinant 1. - Max Alekseyev, Nov 06 2022
LINKS
Jessie MacWilliams, Orthogonal Matrices Over Finite Fields, The American Mathematical Monthly 76:2 (1969), 152-164.
FORMULA
a(2k+1) = 11^k * Product_{i=0..k-1} (11^(2k) - 11^(2i)); a(2k) = (11^k + (-1)^(k+1)) * Product_{i=1..k-1} (11^(2k) - 11^(2i)) (see MacWilliams, 1969). - Max Alekseyev, Nov 06 2022
PROG
(PARI) { a071309(n) = my(t=n\2); prod(i=0, t-1, 11^(2*t)-11^(2*i)) * if(n%2, 11^t, 1/(11^t+(-1)^t)); } \\ Max Alekseyev, Nov 06 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jun 11 2002
EXTENSIONS
Terms a(6) onward from Max Alekseyev, Nov 06 2022
STATUS
approved