OFFSET
0,3
LINKS
FORMULA
a(n) = sum {1*s_1+2*s_2+...=n, 1*t_1+2*t_2+...=n, 1*u_1+2*u_2=2} (fixA[s_1, s_2, ...;t_1, t_2, ...;u_1, u_2] /(1^s_1*s_1!*2^s_2*s_2!*... *1^t_1*t_1!*2^t_2*t_2!*... *1^u_1*u_1!*2^u_2*u_2!)) where fixA[...] = prod {i, j>=1} ( (sum {d|lcm(i, j)} (d*u_d))^(gcd(i, j)*s_i*t_j)).
CROSSREFS
KEYWORD
nonn
AUTHOR
Christian G. Bower, Dec 17 2003
EXTENSIONS
a(15) from Alois P. Heinz, Aug 14 2014
STATUS
approved