OFFSET

0,1

COMMENTS

If G is k-regular, then L(G) is (2k-2)-regular. From this it is easy to get the formula for a(n).

FORMULA

a(0)=4 and for n >= 1 a(n) = 4 * product k=1...n (1+2^(k-2))

EXAMPLE

The line graph of the complete graph on 4 vertices has C(4,2) vertices so a(1) = 6.

MAPLE

for n from 0 to 30 do printf(`%d, `, 4*product(1+2^(k-2), k=1..n)) od:

CROSSREFS

KEYWORD

nonn

AUTHOR

Avi Peretz (njk(AT)netvision.net.il), Mar 18 2001

EXTENSIONS

More terms from James A. Sellers and Vladeta Jovovic, Mar 26 2001

STATUS

approved