A138908 - OEIS

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A138908

a(n) = d^d, where d is the number of digits in n.

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,11

LINKS

Table of n, a(n) for n=0..120.

FORMULA

From Amiram Eldar, Nov 18 2020: (Start)

a(n) = A055642(n)^A055642(n).

Sum_{n>=1} 1/a(n) = A308314. (End)

MATHEMATICA

dd[n_]:=Module[{d=IntegerLength[n]}, d^d]; Join[{1}, Array[dd, 150]] (* Harvey P. Dale, Mar 16 2013 *)

PROG