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A297173 Smallest difference between indices of prime divisors of n, or 0 if n is a prime power.

%I A297173 #7 Mar 03 2018 09:52:49
%S A297173 0,0,0,0,0,1,0,0,0,2,0,1,0,3,1,0,0,1,0,2,2,4,0,1,0,5,0,3,0,1,0,0,3,6,
%T A297173 1,1,0,7,4,2,0,1,0,4,1,8,0,1,0,2,5,5,0,1,2,3,6,9,0,1,0,10,2,0,3,1,0,6,
%U A297173 7,1,0,1,0,11,1,7,1,1,0,2,0,12,0,1,4,13,8,4,0,1,2,8,9,14,5,1,0,3,3,2,0,1,0,5,1
%N A297173 Smallest difference between indices of prime divisors of n, or 0 if n is a prime power.
%H A297173 Antti Karttunen, <a href="/A297173/b297173.txt">Table of n, a(n) for n = 1..65537</a>
%H A297173 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%F A297173 a(A073491(n)) <= 1.
%e A297173 For n = 130 = 2*5*13 = prime(1)*prime(3)*prime(6), the smallest difference between indices is 3-1 = 2, thus a(130) = 2.
%o A297173 (PARI) A297173(n) = if(omega(n)<=1,0,my(ps=factor(n)[,1]); vecmin(vector((#ps)-1,i,primepi(ps[i+1])-primepi(ps[i]))));
%Y A297173 Cf. A000720, A073490, A073491.
%Y A297173 Cf. also A100573, A243055, A242411, A261079, A286470, A286471.
%K A297173 nonn
%O A297173 1,10
%A A297173 _Antti Karttunen_, Mar 03 2018