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A239009
Exponents m such that the decimal expansion of 4^m exhibits its first zero from the right later than any previous exponent.
7
0, 2, 4, 7, 9, 12, 14, 16, 17, 23, 34, 36, 38, 43, 77, 88, 216, 350, 979, 24186, 28678, 134759, 205829, 374627, 2200364, 16625243, 29451854, 162613199, 8078176309, 9252290259, 17556077280, 49718535383, 51616746477, 54585993918
OFFSET
1,2
COMMENTS
Assume that a zero precedes all decimal expansions. This will take care of those cases in A030701.
Inspired by the seqfan list discussion Re: "possible sequence", beginning with David Wilson 7:57 PM Mar 06 2014 and continued by M. F. Hasler, Allan C. Wechsler and Franklin T. Adams-Watters.
Not just twice A031142, although {16625243, 29451854, 162613199, 9252290259, 51616746477, 54585993918, 146235898847, 1360645542292} are possible candidates.
Location of first zeros (from the right) of terms: 2, 3, 4, 6, 7, 9, 10, 11, 12, 13, 14, 23, 24, 27, 30, 39, 53, 58, 94, 113, 120, 121, 122, 139, 165, 177, 192, 213, 217, 228, 229, 230, 250, 251. - Chai Wah Wu, Jan 08 2020
MATHEMATICA
f[n_] := Position[ Reverse@ Join[{0}, IntegerDigits[ PowerMod[4, n, 10^500]]], 0, 1, 1][[1, 1]]; k = mx = 0; lst = {}; While[k < 100000001, c = f[k]; If[c > mx, mx = c; AppendTo[ lst, k]; Print@ k]; k++]; lst
KEYWORD
nonn,base,more
EXTENSIONS
a(28)-a(30) from Bert Dobbelaere, Jan 21 2019
a(31)-a(34) from Chai Wah Wu, Jan 08 2020
STATUS
approved