%I #9 Apr 21 2021 15:39:57
%S -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,
%T 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,
%U 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
%N a(n) = Sum_{k=1..n} (-1)^A001622(k).
%C A cumulative sum over the parities of the decimals in the decimal expansion of the golden ratio A001622.
%e a(7) = -1 because, with 7 digits of phi = 1.618033... we obtain:
%e (-1)^1 + (-1)^6 + (-1)^1 + (-1)^8 + (-1)^0 + (-1)^3 + (-1)^3 = -1.
%t Rest@ FoldList[ Plus, 0, (-1)^First@ RealDigits[GoldenRatio, 10, 200]]
%Y Cf. A001622.
%K sign,base,less
%O 1,8
%A _Michel Lagneau_, Sep 10 2010