A294390 a(n) = 2^(n-4) mod n, for n >= 4.

1, 2, 4, 1, 0, 5, 4, 7, 4, 5, 2, 8, 0, 15, 4, 12, 16, 11, 14, 3, 16, 2, 10, 5, 8, 11, 4, 4, 0, 17, 30, 23, 4, 14, 24, 20, 16, 36, 4, 27, 12, 32, 6, 6, 16, 8, 14, 26, 40, 20, 22, 13, 16, 29, 22, 37, 16, 23, 8, 32, 0, 2, 4, 42, 52, 35, 64, 9, 40, 64, 28, 23, 20, 30, 4

Offset

4,2

Comments

Every nonnegative integer seems to appear in the sequence, and every integer seems to appear in the sequence of first differences (see link).

From Robert Israel, Dec 04 2017: (Start)

a(n)=0 iff n>=8 is a power of 2.

a(n)=1 iff n=4 or n is in A033984.

a(n)=2 iff n>=4 is in A015925 and is not divisible by 4. (End)

Links

Robert Israel, Table of n, a(n) for n = 4..10000

Enrique Navarrete, Sequences derived from residues of 2^n (mod n)

Example

For n=9, 2^5 = 32 == 5 mod 9.

Maple

A294390:=n->2&^(n-4) mod n: seq(A294390(n), n=4..150); # Wesley Ivan Hurt, Nov 30 2017

Mathematica

Array[Mod[2^(# - 4), #] &, 75, 4] (* Michael De Vlieger, Dec 02 2017 *)
Array[PowerMod[2, #-4, #]&, 80, 4] (* Harvey P. Dale, Dec 01 2018 *)

Prog

(PARI) a(n) = lift(Mod(2, n)^(n-4)); \\ Michel Marcus, Oct 30 2017

Crossrefs

Cf. A015910, A015925, A033984, A294389.

Sequence in context: A124091 A067849 A164268 * A152433 A094344 A211183

Adjacent sequences: A294387 A294388 A294389 * A294391 A294392 A294393

Keyword

nonn,easy,look

Author

Enrique Navarrete, Oct 29 2017

Extensions

More terms from Michel Marcus, Oct 30 2017

Status

approved