A053842 (Sum of digits of n written in base 7) modulo 7.

0, 1, 2, 3, 4, 5, 6, 1, 2, 3, 4, 5, 6, 0, 2, 3, 4, 5, 6, 0, 1, 3, 4, 5, 6, 0, 1, 2, 4, 5, 6, 0, 1, 2, 3, 5, 6, 0, 1, 2, 3, 4, 6, 0, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 6, 0, 2, 3, 4, 5, 6, 0, 1, 3, 4, 5, 6, 0, 1, 2, 4, 5, 6, 0, 1, 2, 3, 5, 6, 0, 1, 2, 3, 4, 6, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 2, 3, 4, 5, 6, 0, 1