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A097975 a(n) is the prime divisor of n which is >= sqrt(n), or 0 if there is no such prime divisor.

%I A097975 #20 Dec 23 2017 04:20:06
%S A097975 0,2,3,2,5,3,7,0,3,5,11,0,13,7,5,0,17,0,19,5,7,11,23,0,5,13,0,7,29,0,
%T A097975 31,0,11,17,7,0,37,19,13,0,41,7,43,11,0,23,47,0,7,0,17,13,53,0,11,0,
%U A097975 19,29,59,0,61,31,0,0,13,11,67,17,23,0,71,0,73,37,0,19,11,13,79,0,0,41,83
%N A097975 a(n) is the prime divisor of n which is >= sqrt(n), or 0 if there is no such prime divisor.
%C A097975 Sequence also is the sum of distinct prime divisors of n which are >= sqrt(n). At most one prime divisor of n is >= square root of n.
%H A097975 Diana Mecum, <a href="/A097975/b097975.txt">Table of n, a(n) for n = 1..1000</a>
%t A097975 Do[l = Select[Select[Divisors[n], PrimeQ], # >= Sqrt[n]&]; If[Length[l] == 0, Print[0], Print[l[[1]]]], {n, 1, 50}] (* _Ryan Propper_, Jul 24 2005 *)
%t A097975 Array[Select[FactorInteger[#][[All, 1]], Function[p, p >= Sqrt@ #]] /. {{} -> {0}, {1} -> {0}} &, 83][[All, 1]] (* _Michael De Vlieger_, Dec 22 2017 *)
%o A097975 (PARI) a(n) = sumdiv(n, d, if (isprime(d) && (d^2 >= n), d)); \\ _Michel Marcus_, Dec 23 2017
%Y A097975 Cf. A097974.
%K A097975 nonn
%O A097975 1,2
%A A097975 _Leroy Quet_, Sep 07 2004
%E A097975 More terms from _Ryan Propper_, Jul 24 2005
%E A097975 More terms from _Stefan Steinerberger_, Jan 21 2006
%E A097975 Further terms from _Diana L. Mecum_, Jun 15 2007