A088387 in OEIS spf(n) is the prime corresponding to largest prime power factor of n, a(1)=1.
Most significant prime factor of n: If n = (p_1^e_1)(p_2^e_2)(p_3^e_3)... and max(p_1^e_1,p_2^e_2,...) = p_k^e_k then spf(n) = p_k.