OFFSET
0,3
COMMENTS
Also relations considered equivalent when isomorphic and when complemented. - Christian G. Bower, Jan 05 2004
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..50
FORMULA
a(n) = sum {1*s_1+2*s_2+...=n, 1*t_1+2*t_2=2} (fixA[s_1, s_2, ...;t_1, t_2]/(1^s_1*s_1!*2^s_2*s_2!*...*1^t_1*t_1!*2^t_2*t_2!)) where fixA[...] = prod {i, j>=1} ( (sum {d|lcm(i, j)} (d*t_d))^(gcd(i, j)*s_i*s_j)) - Christian G. Bower, Jan 05 2004
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Vladeta Jovovic, Jul 19 2000
EXTENSIONS
a(0)=1 prepended and terms a(13) and beyond from Andrew Howroyd, Apr 19 2020
STATUS
approved