login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A036295 Numerator of Sum i/2^i, i=1..n. 4
0, 1, 1, 11, 13, 57, 15, 247, 251, 1013, 509, 4083, 4089, 16369, 2047, 65519, 65527, 262125, 131067, 1048555, 1048565, 4194281, 1048573, 16777191, 16777203, 67108837, 33554425, 268435427, 268435441, 1073741793, 67108863, 4294967263, 4294967279, 17179869149 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

The sum equals 2-(n+2)/2^n.

REFERENCES

C. C. Clawson, The Beauty and Magic of Numbers. New York: Plenum Press (1996): 95

LINKS

Colin Barker, Table of n, a(n) for n = 0..1000

A. F. Horadam, Oresme numbers, Fib. Quart., 12 (1974), 267-271.

FORMULA

If n+2=2^k*m with m odd, then a(n)=2^(n+1-k)-m.

MATHEMATICA

a[n_] := Module[{k, m}, For[k = 0; m = n + 2, EvenQ[m], k++, m/=2]; 2^(n + 1 - k) - m]

Table[Numerator[Sum[i/2^i, {i, n}], {n, 40}] (* Alonso del Arte, Aug 12 2012 *)

PROG

(PARI) concat(0, vector(100, n, numerator(sum(i=1, n, i/2^i)))) \\ Colin Barker, Nov 09 2014

(MAGMA) [0] cat [Numerator(&+[i/2^i: i in [1..n]]): n in [1..40]]; // Vincenzo Librandi, Nov 09 2014

CROSSREFS

Cf. A036296 (denominators).

Sequence in context: A188386 A027450 A234799 * A132201 A057189 A072580

Adjacent sequences:  A036292 A036293 A036294 * A036296 A036297 A036298

KEYWORD

nonn,easy,frac

AUTHOR

N. J. A. Sloane.

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 21 04:18 EST 2019. Contains 320371 sequences. (Running on oeis4.)