%I #15 Jun 18 2013 15:25:13
%S 2,5,8,17,20,32,65,68,80,128,257,260,272,320,512,1025,1028,1040,1088,
%T 1280,2048,4097,4100,4112,4160,4352,5120,8192,16385,16388,16400,16448,
%U 16640,17408,20480,32768,65537,65540,65552,65600,65792,66560,69632,81920,131072
%N Sums of two powers of 4.
%H T. D. Noe, <a href="/A055236/b055236.txt">Rows n = 0..100 of triangle, flattened</a>
%F a(n) = 4^(n-trinv(n))+4^trinv(n), where trinv(n) = floor((1+sqrt(1+8*n))/2) = A002262(n) and n-trinv(n) = A003056(n).
%F Regarded as a triangle T(n, k) = 4^n + 4^k, so as a sequence a(n) = 4^A002262(n) + 4^A003056(n).
%t t = 4^Range[0, 9]; Select[Union[Flatten[Table[i + j, {i, t}, {j, t}]]], # <= t[[-1]] + 1 &] (* _T. D. Noe_, Oct 09 2011 *)
%t Union[Total/@Tuples[4^Range[0,9], 2]] (* _Harvey P. Dale_, Mar 25 2012 *)
%Y Cf. A052216.
%K easy,nonn,tabl
%O 0,1
%A _Henry Bottomley_, Jun 22 2000