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%I #10 Oct 17 2016 12:00:17
%S 1,3,17,41,125,321,745,1777,4089,9217,20417,45009,98273,212977,458753,
%T 982881,2097025,4456353,9437121,19922913,41943041,88080001,184549057,
%U 385875713,805306177,1677721473,3489660865,7247757313,15032384641,31138512129,64424508801
%N a(n) = Sum{i=1..n} ( i*2^(i-1) ) - ( A002024(n)*(A002024(n)+1)/2 - n ) * 2^(A002024(n)-1).
%C At one time this expression was proposed (erroneously) as a formula for A007664.
%H G. C. Greubel, <a href="/A135471/b135471.txt">Table of n, a(n) for n = 1..1000</a>
%t f[n_] := Floor[Sqrt[2*n] + 1/2]; a[n_] := Sum[ i*2^(i - 1), {i, 1, n}] - (f[n]*(f[n] + 1)/2 - n)*2^(f[n] - 1); Table[a[n], {n, 1, 25}] (* _G. C. Greubel_, Oct 14 2016 *)
%Y Cf. A007664.
%K nonn
%O 1,2
%A _N. J. A. Sloane_, Feb 08 2008
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