A215747 a(n) = (-2)^n mod n.

0, 0, 1, 0, 3, 4, 5, 0, 1, 4, 9, 4, 11, 4, 7, 0, 15, 10, 17, 16, 13, 4, 21, 16, 18, 4, 1, 16, 27, 4, 29, 0, 25, 4, 17, 28, 35, 4, 31, 16, 39, 22, 41, 16, 28, 4, 45, 16, 19, 24, 43, 16, 51, 28, 12, 32, 49, 4, 57, 16, 59, 4, 55, 0, 33, 64, 65, 16, 61, 44, 69, 64, 71, 4, 7

Offset

1,5

Comments

n^(n+2) mod (n+2) is essentially the same.

Indices of 0's: 2^k - 1, k>=0.

Indices of 1's: A006521 except the first term.

Indices of 3's: A015940.

Indices of 5's: 7, 133, 1517, 11761, ...

a(A000040(n)) = A000040(n)-2 = A040976(n).

Links

Alois P. Heinz, Table of n, a(n) for n = 1..10000

Example

a(5) = (-2)^5 mod 5 = -32 mod 5 = 3.

Maple

a:= n-> (-2)&^n mod n:
seq(a(n), n=1..100);  # Alois P. Heinz, Apr 08 2015

Prog

(Python)
for n in range(1, 333):
    print((-2)**n % n, end=', ')

Crossrefs

Cf. A015910, A082493, A082494, A110146, A213381.

Sequence in context: A100649 A158962 A263824 * A246667 A199066 A306584

Adjacent sequences: A215744 A215745 A215746 * A215748 A215749 A215750

Keyword

nonn,look

Author

Alex Ratushnyak, Aug 23 2012

Status

approved