A239062 - OEIS

A239062

Number of integers x, 1 <= x <= n, such that x^x == 0 (mod n).

1, 1, 1, 2, 1, 1, 1, 3, 3, 1, 1, 2, 1, 1, 1, 7, 1, 3, 1, 2, 1, 1, 1, 4, 5, 1, 9, 2, 1, 1, 1, 15, 1, 1, 1, 6, 1, 1, 1, 4, 1, 1, 1, 2, 3, 1, 1, 8, 7, 5, 1, 2, 1, 9, 1, 4, 1, 1, 1, 2, 1, 1, 3, 31, 1, 1, 1, 2, 1, 1, 1, 12, 1, 1, 5, 2, 1, 1, 1, 8, 26, 1, 1, 2, 1, 1, 1, 4, 1, 3, 1, 2, 1, 1, 1, 16, 1, 7, 3, 10, 1, 1, 1, 4, 1

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

OFFSET

1,4

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

EXAMPLE

From Michael De Vlieger, Sep 23 2017: (Start)

Table of records a(n) and first positions n:

i n a(n)

-------------------

1 1 1

2 4 2

3 8 3

4 16 7

5 27 9

6 32 15

7 64 31

8 128 62

9 243 80

10 256 126

11 512 253

12 1024 509

13 2048 1020

14 4096 2044

15 6561 2185

16 8192 4092

17 16384 8188

(End)

MATHEMATICA

gg0[n_] := Sum[If[Mod[x^x , n] == 0, 1, 0], {x, n}]; Array[gg0, 200]

(* or *)

Array[Sum[Boole[PowerMod[x, x, #] == 0], {x, #}] &, 10^4] (* or *)

Table[Count[Range@ n, k_ /; PowerMod[k, k, n] == 0], {n, 200}] (* Michael De Vlieger, Sep 23 2017 *)

PROG

(PARI) A239062(n) = sum(x=1, n, if(0 == Mod(x^x, n), 1, 0)); \\ Antti Karttunen, Sep 23 2017, after the Mathematica-program.

CROSSREFS

Cf. A239061, A239063, A005117 (indices of 1's).

Sequence in context: A152798 A079115 A072906 * A341052 A201160 A302538

Adjacent sequences: A239059 A239060 A239061 * A239063 A239064 A239065

KEYWORD

nonn

AUTHOR

José María Grau Ribas, Mar 09 2014

EXTENSIONS

More terms from Antti Karttunen, Sep 23 2017

STATUS

approved