A239012 Exponents m such that the decimal expansion of 7^m exhibits its first zero from the right later than any previous exponent.

0, 2, 3, 6, 10, 11, 19, 35, 127, 131, 175, 207, 1235, 2470, 2651, 1241310, 1922910, 471056338, 1001431598, 1720335627, 4203146094, 5353516238, 21838571507, 25770284079, 40822793867

Offset

1,2

Comments

Assume that a zero precedes all decimal expansions. This will take care of those cases in A030703.

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.

Links

Table of n, a(n) for n=1..25.

Mathematica

f[n_] := Position[ Reverse@ Join[{0}, IntegerDigits[ PowerMod[7, n, 10^500]]], 0, 1, 1][[1, 1]]; k = mx = 0; lst = {}; While[k < 500000001, c = f[k]; If[c > mx, mx = c; AppendTo[ lst, k]; Print@ k]; k++]; lst

Crossrefs

Cf. A000420, A030703, A020665, A031142, A239008, A239009, A239010, A239011, A239013, A239014, A239015.

Sequence in context: A088196 A112925 A193246 * A001635 A106172 A189478

Adjacent sequences: A239009 A239010 A239011 * A239013 A239014 A239015

Keyword

nonn,base,more

Author

Charles R Greathouse IV and Robert G. Wilson v, Mar 14 2014

Extensions

a(19)-a(22) from Bert Dobbelaere, Jan 21 2019

a(23)-a(25) from Chai Wah Wu, Jan 15 2020

Status

approved