1,4
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
Sequence in context: A054381 A102088 A088142 * A009343 A048175 A192482
Adjacent sequences: A049367 A049368 A049369 * A049371 A049372 A049373
nonn,nice,hard
Brendan McKay (bdm(AT)cs.anu.edu.au)