|
|
A292411
|
|
a(n) = ((prime(n) - 1)/2)^2 modulo prime(n).
|
|
1
|
|
|
1, 4, 2, 3, 10, 13, 5, 6, 22, 8, 28, 31, 11, 12, 40, 15, 46, 17, 18, 55, 20, 21, 67, 73, 76, 26, 27, 82, 85, 32, 33, 103, 35, 112, 38, 118, 41, 42, 130, 45, 136, 48, 145, 148, 50, 53, 56, 57, 172, 175, 60, 181, 63, 193, 66, 202, 68, 208, 211, 71, 220, 77, 78, 235, 238, 83, 253, 87, 262
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
2,2
|
|
COMMENTS
|
Also the square of (prime(n) - 1)/2 + 1 modulo prime(n).
|
|
LINKS
|
|
|
EXAMPLE
|
The fourth prime is 7; ((7 - 1)/2)^2 = 3^2 = 9 = 2 mod 7. Hence a(4) = 2.
The fifth prime is 11; ((11 - 1)/2)^2 = 5^2 = 25 = 3 mod 11. Hence a(5) = 3.
|
|
MATHEMATICA
|
Table[PowerMod[(Prime[n] - 1)/2, 2, Prime[n]], {n, 2, 70}]
|
|
PROG
|
(PARI) a(n) = lift(Mod((prime(n)-1)/2, prime(n))^2); \\ Michel Marcus, Sep 19 2017
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,easy
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|