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%I #13 Mar 04 2023 19:29:00
%S 0,1,3,7,15,31,39,45,63,78,79,91,93,127,139,143,158,159,175,182,187,
%T 189,222,255,286,287,318,319,351,367,375,379,381,407,446,487,511,535,
%U 543,572,574,575,607,627,638,639,703,724,727,731,747,750,759,763,765,799,823,830
%N Numbers m such that B(m) = B(triangular(m)), where B(m) is the binary weight of m (A000120).
%H Dumitru Damian, <a href="/A212315/b212315.txt">Table of n, a(n) for n = 1..10000</a>
%F A000120(a(n)) = A000120(a(n)*(a(n)+1)/2).
%o (Python)
%o def isa(n): return n.bit_count()==((n*(n+1))>>1).bit_count()
%o print(list(n for n in range(10**3) if isa(n))) # _Dumitru Damian_, Mar 04 2023
%Y Cf. A000120, A077436, A083567, A118655, A212314.
%K nonn,base,easy
%O 1,3
%A _Alex Ratushnyak_, Oct 24 2013