A337380 - OEIS

%I #6 Aug 27 2020 17:08:27

%S 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,1,0,0,0,0,1,0,0,

%T 0,1,0,0,0,1,0,0,0,0,1,0,0,1,1,0,0,0,0,1,0,1,0,0,0,0,0,0,1,1,0,0,0,0,

%U 0,0,0,1,0,0,0,0,0,0,0,1,1,0,0,1,0,0,0,0,0,1,0,0,0,0,0,1,0,1,1,1,0,0,0,1,1

%N a(n) = 1 if A003961(n) > 2*sigma(n), 0 otherwise.

%H Antti Karttunen, <a href="/A337380/b337380.txt">Table of n, a(n) for n = 1..65537</a>

%H <a href="/index/Ch#char_fns">Index entries for characteristic functions</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>

%o (PARI)

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

%o A337380(n) = (A003961(n)>2*sigma(n));

%Y Cf. A000203, A003961, A337379.

%Y Characteristic function of A337378.

%Y Cf. also A252742, A337383.

%K nonn

%O 1

%A _Antti Karttunen_, Aug 27 2020