The first term of the series is FOUR [why do you say 2 ??]
2000000 = 4 * [(1 - 2^n) / (1 - 2)]
500000 - 1 = 2^n
499999 = 2^n
n = [log 499999] / [log 2] ≈ 18.931565683931206915366131383779
now multiply by 4...
4(18.93157) ≈ 75.72628 [rounded to 76 days ]
δ
2000000 = 4 * [(1 - 2^n) / (1 - 2)]
500000 - 1 = 2^n
499999 = 2^n
n = [log 499999] / [log 2] ≈ 18.931565683931206915366131383779
now multiply by 4...
4(18.93157) ≈ 75.72628 [rounded to 76 days ]
δ