D # f[m_] := Apply[BitXor, Table[n, {n, 1, m}]] # f /@ Range[50] # FindSequenceFunction[%, n] // FullSimplify # https://oeis.org/A003815 # a(0)=0, a(4n+1)=1, a(4n+2)=4n+3, a(4n+3)=0, a(4n+4)=4n+4, n >= 0. def a(n): if n == 0: return 0 elif n % 4 == 1: return 1 elif n % 4 == 2: return n ^ (n + 1) ...