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 A050493 a(n) = sum of binary digits of n-th triangular number. 2
 0, 1, 2, 2, 2, 4, 3, 3, 2, 4, 5, 2, 4, 5, 4, 4, 2, 4, 5, 6, 4, 6, 7, 3, 4, 4, 7, 6, 5, 6, 5, 5, 2, 4, 5, 6, 5, 8, 6, 4, 5, 7, 6, 6, 8, 4, 5, 4, 4, 5, 8, 6, 5, 7, 7, 3, 6, 7, 8, 7, 6, 7, 6, 6, 2, 4, 5, 6, 5, 8, 7, 8, 4, 6, 8, 5, 8, 9, 4, 5, 5, 8, 7, 8, 8, 7, 8, 8, 7, 8, 12, 5, 6, 5, 6, 5, 4, 5, 8, 7, 8 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS See A211201 for smallest numbers m such that a(m) = n. - Reinhard Zumkeller, Feb 04 2013 LINKS T. D. Noe, Table of n, a(n) for n = 0..1024 FORMULA a(n) = Sum_{i=1..floor(log_b(c(n)))+1} (floor(c(n)/b^(i-1)) - floor(c(n)/b^i)*b), b=2, n >= 1, a(0)=0, c(n)=A000217(n). a(n) = A000120(A000217(n)). - Reinhard Zumkeller, Feb 04 2013 a(n) = [x^(n*(n+1)/2)] (1/(1 - x))*Sum_{k>=0} x^(2^k)/(1 + x^(2^k)). - Ilya Gutkovskiy, Mar 27 2018 MATHEMATICA f[n_]:=Plus@@IntegerDigits[n, 2]; lst={}; Do[t=n*(n+1)/2; AppendTo[lst, f[t]], {n, 6!}]; lst (* Vladimir Joseph Stephan Orlovsky, Oct 10 2009 *) Total[IntegerDigits[#, 2]]&/@Accumulate[Range[0, 100]] (* Harvey P. Dale, Jan 22 2012 *) PROG (Haskell) a050493 = a000120 . a000217  -- Reinhard Zumkeller, Feb 04 2013 (PARI) a(n)=hammingweight(n*(n+1)) \\ Charles R Greathouse IV, Nov 10 2015 CROSSREFS Cf. A000120, A000217, A004157. Sequence in context: A208609 A249030 A257126 * A331851 A335607 A338796 Adjacent sequences:  A050490 A050491 A050492 * A050494 A050495 A050496 KEYWORD base,easy,nice,nonn AUTHOR Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Dec 27 1999 STATUS approved

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Last modified August 1 03:52 EDT 2021. Contains 346384 sequences. (Running on oeis4.)