%I #11 Apr 07 2014 03:11:48
%S 2,17,32,257,272,512,4097,4112,4352,8192,65537,65552,65792,69632,
%T 131072,1048577,1048592,1048832,1052672,1114112,2097152,16777217,
%U 16777232,16777472,16781312,16842752,17825792,33554432,268435457
%N Sums of two powers of 16.
%H Robert Israel, <a href="/A055261/b055261.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = 16^(n-trinv(n))+16^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)=16^n+16^k, so as a sequence a(n) =16^A002262(n)+16^A003056(n).
%e a(4) = 272 = 16^2+16^1.
%p A055261:= proc(n)
%p local p1, p2;
%p p1:= floor((sqrt(8*n-7)-1)/2);
%p p2:= n - 1 - p1*(p1+1)/2;
%p 16^p1 + 16^p2
%p end proc; # _Robert Israel_, Apr 07 2014
%Y Cf. A052216.
%K base,easy,nonn,tabl
%O 1,1
%A _Henry Bottomley_, Jun 22 2000