A336846 - OEIS

%I #14 Aug 08 2020 11:30:58

%S 1,2,2,1,2,12,2,4,1,4,2,6,2,12,4,1,2,2,2,2,4,4,2,120,3,12,4,6,2,24,2,

%T 2,4,4,4,1,2,12,4,8,2,24,2,26,2,12,2,6,1,6,20,18,2,24,28,24,4,4,2,12,

%U 2,4,6,1,4,24,2,2,20,24,2,20,2,12,6,6,4,24,2,2,1,4,2,36,4,12,4,8,2,4,4,6,4,12,4,12,2,2,2,3

%N a(n) = gcd(sigma(A003961(n)), A000005(n)*A003961(n)).

%H Antti Karttunen, <a href="/A336846/b336846.txt">Table of n, a(n) for n = 1..16384</a>

%H Antti Karttunen, <a href="/A336846/a336846.txt">Data supplement: n, a(n) computed for n = 1..65537</a>

%H <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>

%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>

%F a(n) = gcd(A003973(n), A336845(n)) = gcd(A003973(n), A336841(n)).

%F a(n) = gcd(A000203(A003961(n)), A000005(n)*A003961(n)).

%F a(n) = A324121(A003961(n)).

%o (PARI)

%o A003961(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };

%o A336846(n) = { my(u=A003961(n),s=sigma(u)); gcd(s, numdiv(n)*u); };

%Y Cf. A000005, A000203, A000290 (positions of odd terms), A003961, A003973, A324121, A336476, A336841, A336845, A336847, A336848.

%K nonn

%O 1,2

%A _Antti Karttunen_, Aug 06 2020