cp's OEIS Frontend

A336919 Numbers k such that A000005(k) does not divide A003973(k); numbers k for which A336839(k) > 1.

%I A336919 #6 Aug 17 2020 20:52:14
%S A336919 4,9,16,18,20,32,36,44,45,48,49,64,68,72,80,81,90,98,99,100,112,116,
%T A336919 124,144,153,160,162,164,169,176,180,192,196,198,208,220,225,236,240,
%U A336919 244,245,252,256,261,279,284,288,292,304,306,320,324,336,338,340,352,356,360,361,369,392,396,400,404,405,428,432,441
%N A336919 Numbers k such that A000005(k) does not divide A003973(k); numbers k for which A336839(k) > 1.
%C A336919 Numbers k such that A003961(k) is not in A003601, but in A049642.
%H A336919 Antti Karttunen, <a href="/A336919/b336919.txt">Table of n, a(n) for n = 1..20000</a>
%H A336919 <a href="/index/Pri#prime_indices">Index entries for sequences computed from indices in prime factorization</a>
%o A336919 (PARI)
%o A336919 A003961(n) = { my(f = factor(n)); for(i=1, #f~, f[i, 1] = nextprime(f[i, 1]+1)); factorback(f); };
%o A336919 isA336919(n) = !!(sigma(A003961(n))%numdiv(n));
%Y A336919 Cf. A000005, A003601, A003961, A003973, A049642, A336839.
%Y A336919 Cf. A336918 (complement).
%K A336919 nonn
%O A336919 1,1
%A A336919 _Antti Karttunen_, Aug 12 2020