A175816 a(n) = Sum_{k=1..n} (-1)^A001622(k).

-1, 0, -1, 0, 1, 0, -1, -2, -1, 0, -1, 0, -1, 0, -1, 0, 1, 2, 3, 4, 5, 6, 5, 6, 7, 8, 7, 8, 7, 8, 7, 8, 7, 8, 7, 6, 5, 4, 5, 6, 5, 6, 5, 4, 3, 2, 3, 4, 3, 2, 3, 4, 5, 6, 7, 6, 5, 4, 5, 6, 7, 8, 9, 10, 9, 10, 9, 10, 11, 12, 13, 14, 15, 16, 15, 16, 15, 16, 17, 18, 19, 18, 17, 18, 17, 18, 19, 18, 19

Offset

1,8

Comments

A cumulative sum over the parities of the decimals in the decimal expansion of the golden ratio A001622.

Links

Table of n, a(n) for n=1..89.

Example

a(7) = -1 because, with 7 digits of phi = 1.618033... we obtain:
(-1)^1 + (-1)^6 + (-1)^1 + (-1)^8 + (-1)^0 + (-1)^3 + (-1)^3 = -1.

Mathematica

Rest@ FoldList[ Plus, 0, (-1)^First@ RealDigits[GoldenRatio, 10, 200]]

Crossrefs

Cf. A001622.

Sequence in context: A331218 A120086 A215030 * A227573 A085004 A095774

Adjacent sequences: A175813 A175814 A175815 * A175817 A175818 A175819

Keyword

sign,base,less

Author

Michel Lagneau, Sep 10 2010

Status

approved