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

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

(PARI) a(n) = my(d=#Str(n)); d^d; \\ Michel Marcus, Nov 18 2020

Crossrefs

Cf. A055642, A138902, A308314.

Sequence in context: A251539 A123932 A010709 * A032564 A141248 A273339

Adjacent sequences: A138905 A138906 A138907 * A138909 A138910 A138911

Keyword

easy,nonn,base

Author

Odimar Fabeny, May 16 2008

Extensions

Edited by N. J. A. Sloane, Sep 29 2011, at the suggestion of Franklin T. Adams-Watters

Status

approved