OFFSET
1,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..200
MATHEMATICA
Take[Union@Flatten@Table[BellB[i] BellB[j], {i, 0, 60}, {j, i}], 60]
PROG
(Perl) use ntheory ":all"; my($l, $i, %BP)=(50, 0); my @Bell = map { my $n=$_; vecsum(map { stirling($n, $_, 2) } 0..$n); } 0..$l; for my $i (0..$l) { for my $j ($i..$l) { $BP{vecprod($Bell[$i], $Bell[$j])}++ } } say $i++, " $_" for sort {$a<=>$b} keys %BP; # Dana Jacobsen, Sep 07 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Sep 04 2016
STATUS
approved