1,2

1(=(product_{x=0..2} x)/2), 3(=(product_{x=1..3} x)/2), 10(=(product_{x=4..5} x)/2), 21(=(product_{x=6..7} x)/2), 3960(=(product_{x=8..11} x)/2), etc.

Cf. A000040, A141468.

Sequence in context: A158030 A068082 A058077 this_sequence A122795 A140066 A006503

Adjacent sequences: A161669 A161670 A161671 this_sequence A161673 A161674 A161675

nonn,uned

Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jun 16 2009