|
%I #20 Dec 03 2015 04:31:04
%S 1,10,39,148,405,1254,3143,8488,20853,52050,123915,297804,692237,
%T 1611974,3687795,8405584,18939921,42512562,94634003,209819940,
%U 462431697,1015269486,2218786839,4832458392,10485762025,22684180610,48922424415,105229923596
%N a(n) = n * Sum_{d|n} d*2^(d-1).
%H Colin Barker, <a href="/A074225/b074225.txt">Table of n, a(n) for n = 1..1000</a>
%H N. J. A. Sloane and Thomas Wieder, <a href="http://arXiv.org/abs/math.CO/0307064">The Number of Hierarchical Orderings</a>, arXiv:math/0307064 [math.CO], 2003.
%H N. J. A. Sloane and Thomas Wieder, <a href="http://dx.doi.org/10.1007/s11083-004-9460-9">The Number of Hierarchical Orderings</a>, Order 21 (2004), 83-89.
%t a[n_] := n*DivisorSum[n, #*2^(#-1)&]; Array[a, 30] (* _Jean-François Alcover_, Dec 03 2015 *)
%o (PARI) vector(100, n, n*sumdiv(n, d, d*2^(d-1))) \\ _Colin Barker_, Jan 29 2015
%Y Equals n*A083413(n).
%K nonn
%O 1,2
%A _N. J. A. Sloane_, Jun 15 2003
|
