A239684 Number of digits in the decimal expansion of n^4.
1, 1, 2, 2, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8
Offset: 0
Examples
For n=1, a(1)=1 because 1^4=1. For n=5, a(5)=3 because 5^4=625.
Crossrefs
Cf. A055642.
Programs
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Mathematica
Join[{1},IntegerLength[Range[90]^4]] (* Harvey P. Dale, Sep 06 2015 *)
Formula
a(n) = A055642(n^4).