A276281 Numbers of the form Bell(i)*Bell(j).
1, 2, 4, 5, 10, 15, 25, 30, 52, 75, 104, 203, 225, 260, 406, 780, 877, 1015, 1754, 2704, 3045, 4140, 4385, 8280, 10556, 13155, 20700, 21147, 41209, 42294, 45604, 62100, 105735, 115975, 178031, 215280, 231950, 317205, 579875, 678570, 769129, 840420, 1099644
Offset: 1
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..200
Programs
-
Mathematica
Take[Union@Flatten@Table[BellB[i] BellB[j], {i, 0, 60}, {j, i}], 60] -
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