A324053 - OEIS

%I #5 Feb 14 2019 07:47:28

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

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

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

%N a(n) = 1 if n > 3 and A002322(n) divides n-3, 0 otherwise; Characteristic function of 3-Knödel numbers.

%C Characteristic function of A033553, 3-Knödel numbers.

%H Antti Karttunen, <a href="/A324053/b324053.txt">Table of n, a(n) for n = 1..100000</a>

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Kn%C3%B6del_number">Knödel number</a>

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

%o (PARI)

%o A002322(n) = lcm(znstar(n)[2]); \\ From A002322

%o A324053(n) = ((n>3) && 0==((n-3)%A002322(n)));

%o (PARI) A324053(n) = if(n<4,0, my(p=factor(n)); for(i=1, matsize(p)[1], if( (n-3)%eulerphi(p[i, 1]^p[i, 2]), return(0)); ); 1); \\ After _Max Alekseyev_'s code in A033553

%Y Cf. A002322, A033553.

%K nonn

%O 1

%A _Antti Karttunen_, Feb 13 2019