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A089048 Number of ways of writing n as a sum of exactly 3 powers of 2. 3
0, 0, 0, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 1, 0, 1, 1, 2, 1, 2, 1, 1, 0, 2, 1, 1, 0, 1, 0, 0, 0, 1, 1, 2, 1, 2, 1, 1, 0, 2, 1, 1, 0, 1, 0, 0, 0, 2, 1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 1, 2, 1, 1, 0, 2, 1, 1, 0, 1, 0, 0, 0, 2, 1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 2, 1, 1, 0, 1, 0, 0, 0, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,7

COMMENTS

The powers do not need to be distinct.

LINKS

Table of n, a(n) for n=0..104.

FORMULA

For n>2: a(n) = (1 + (1 - A000120(n) mod 2)*(1 - n mod 2)) * 0^floor(A000120(n)/4). - Reinhard Zumkeller, Dec 14 2003

MAPLE

f := proc(n, k) option remember; if k > n then RETURN(0); fi; if k= 0 then if n=0 then RETURN(1) else RETURN(0); fi; fi; if n mod 2 = 1 then RETURN(f(n-1, k-1)); fi; f(n-1, k-1)+f(n/2, k); end; # present sequence is f(n, 3)

MATHEMATICA

a[n_] := If[n < 3, 0, ((1 - Mod[n, 2])*(1 - Mod[DigitCount[n, 2, 1], 2]) + 1)*If[Floor[(1/4)*DigitCount[n, 2, 1]] == 0, 1, 0]];

Table[a[n], {n, 0, 104}] (* Jean-Fran├žois Alcover, Feb 13 2018, after Reinhard Zumkeller_ *)

CROSSREFS

A column of A089052. Cf. A036987, A075897, A089049, A089050, A089051, A089053.

Sequence in context: A305054 A238097 A066955 * A263025 A184348 A242481

Adjacent sequences:  A089045 A089046 A089047 * A089049 A089050 A089051

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 03 2003

STATUS

approved

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Last modified May 26 21:55 EDT 2018. Contains 304645 sequences. (Running on oeis4.)