A175792 a(n) = Sum_{k=1..n} (-1)^A000796(k), excess of the number of even over odd digits in the first n digits of Pi.

-1, -2, -1, -2, -3, -4, -3, -2, -3, -4, -5, -4, -5, -6, -7, -8, -7, -8, -7, -6, -5, -4, -3, -2, -3, -4, -3, -4, -3, -4, -5, -6, -5, -4, -3, -2, -1, -2, -3, -4, -5, -4, -5, -6, -7, -8, -9, -10, -11, -12, -11, -12, -11, -10, -9, -10, -11, -10, -11, -10, -9, -10, -11, -10

Offset

1,2

Links

Table of n, a(n) for n=1..64.

Example

a(6) = (-1)^3 + (-1)^1 + (-1)^4 + (-1)^1 + (-1)^5 + (-1)^9= -4.

Maple

Digits := 100:
A000796 := proc(n)
        floor(Pi*10^(n-1)) mod 10;
end proc:
A175792 := proc(n)
        add((-1)^A000796(k), k=1..n) ;
end proc: # R. J. Mathar, Jul 10 2012

Mathematica

Rest@ FoldList[ Plus, 0, (-1)^First@ RealDigits[Pi, 10, 200]]
Accumulate[Table[If[EvenQ[n], 1, -1], {n, RealDigits[Pi, 10, 70][[1]]}]] (* Harvey P. Dale, Nov 03 2015 *)

Crossrefs

cf. A000796, A030657, A196686 (negated), A175813 (indices of 0's).

Sequence in context: A375088 A202275 A030307 * A196686 A213088 A357564

Adjacent sequences: A175789 A175790 A175791 * A175793 A175794 A175795

Keyword

base,sign

Author

Michel Lagneau, Sep 06 2010

Status

approved