A175794 a(n) = Sum_{k=1..n} (-1)^A001620(k).

-1, -2, -3, -2, -3, -4, -3, -2, -1, -2, -1, -2, -3, -4, -3, -2, -1, 0, 1, 2, 3, 2, 1, 2, 3, 2, 3, 4, 5, 6, 7, 8, 9, 10, 9, 8, 9, 10, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 2, 1, 0, -1, 0, 1, 2, 1, 0, 1, 0, 1, 0, 1, 2, 3, 4, 5, 6, 5, 4, 5, 6, 5, 4, 3, 4, 5, 6, 7, 6, 7, 6, 5, 6, 5, 6, 5, 6, 7, 6, 7, 6, 5, 4, 5

Offset: 1

Author

Michel Lagneau, Sep 06 2010

Keywords

• sign
• obsc
• less
• base

Examples

			a(6) = -4 is in the sequence because -4 = (-1)^5 + (-1)^7 + (-1)^7 + (-1)^2 + (-1)^1 + (-1)^5
		

Links

• G. C. Greubel, Table of n, a(n) for n = 1..10000

Crossrefs

A001620 is the decimal expansion of Euler's constant (or Euler-Mascheroni constant) gamma.

Programs

Maple

with(numtheory):T:=array(1..201): Digits:=200:nn:=10^200:a:=floor(evalf(gamma(0))*nn): n:=a:l:=length(n):n0:=n:s:=0:for m from 1 to l do:q:=n0:u:=irem(q,10):v:=iquo(q,10):n0:=v :T[m]:=u:od: for p from l to 1 by -1 do:s:=s+(-1)^T[p]: printf(`%d, `, s):od:

Mathematica

Rest@ FoldList[ Plus, 0, (-1)^First@ RealDigits[EulerGamma, 10, 200]] (* or *) Accumulate[(-1)^RealDigits[EulerGamma,10,100][[1]]] (* Harvey P. Dale, May 11 2014 *)