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A326147 a(n) = gcd(n-A020639(n), sigma(n)-A020639(n)-n), where A020639 gives the smallest prime factor of n, and sigma is the sum of divisors of n.

%I A326147 #8 Jun 12 2019 19:14:34
%S A326147 1,1,2,1,4,4,6,1,1,2,10,2,12,4,6,1,16,1,18,2,2,4,22,2,1,2,2,26,28,4,
%T A326147 30,1,6,2,2,1,36,4,2,2,40,4,42,2,6,4,46,2,1,1,6,2,52,4,2,2,2,2,58,2,
%U A326147 60,4,2,1,2,4,66,2,6,4,70,1,72,2,2,2,2,4,78,26,1,2,82,2,2,4,6,2,88,2,14,2,2,4,10,2,96,1,6,1,100,4,102,2,6
%N A326147 a(n) = gcd(n-A020639(n), sigma(n)-A020639(n)-n), where A020639 gives the smallest prime factor of n, and sigma is the sum of divisors of n.
%H A326147 Antti Karttunen, <a href="/A326147/b326147.txt">Table of n, a(n) for n = 1..20000</a>
%F A326147 a(n) = gcd(n-A020639(n), A000203(n)-A020639(n)-n).
%F A326147 For n > 1, a(n) = gcd(A046666(n), A326146(n)).
%o A326147 (PARI)
%o A326147 A020639(n) = if(1==n, n, factor(n)[1, 1]);
%o A326147 A326147(n) = gcd(n-A020639(n), sigma(n)-A020639(n)-n);
%Y A326147 Cf. A000203, A020639, A046666, A326146, A326148.
%Y A326147 Cf. also A009194, A325385, A325813, A325975, A326046, A326047, A326048, A326056, A326057, A326060, A326062, A326073, A326129, A326130, A326140, A326144.
%K A326147 nonn
%O A326147 1,3
%A A326147 _Antti Karttunen_, Jun 10 2019