A376757 - OEIS

A376757

Number of pairs 0 <= x <= y <= n-1 such that x^3 == y^3 (mod n).

1, 2, 3, 5, 5, 6, 13, 14, 18, 10, 11, 15, 25, 26, 15, 28, 17, 36, 37, 25, 39, 22, 23, 42, 35, 50, 81, 71, 29, 30, 61, 72, 33, 34, 65, 99, 73, 74, 75, 70, 41, 78, 85, 55, 90, 46, 47, 84, 112, 70, 51, 137, 53, 162, 55, 218, 111, 58, 59, 75, 121, 122, 288, 208, 125, 66, 133, 85, 69, 130, 71, 306, 145, 146, 105, 203, 143, 150, 157

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OFFSET

1,2

COMMENTS

A087786 includes pairs (x,y) with x>y (which are excluded from the present sequence).

LINKS

Seiichi Manyama, Table of n, a(n) for n = 1..10000

PROG

(PARI) a(n) = sum(x=0, n-1, sum(y=x, n-1, Mod(x, n)^3 == Mod(y, n)^3)); \\ Michel Marcus, Oct 06 2024

(Python)

from collections import Counter

def A376757(n): return sum(d*(d+1)>>1 for d in Counter(pow(x, 3, n) for x in range(n)).values()) # Chai Wah Wu, Oct 06 2024