A380536 - OEIS

%I #9 Feb 12 2025 14:21:16

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

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

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

%N a(n) = 1 if n is a multiple of A351566(n), otherwise 0, where A351566 is the radix prime of the second least significant nonzero digit in the primorial base expansion of n, or 1 if there is no such digit.

%H Antti Karttunen, <a href="/A380536/b380536.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#primorialbase">Index entries for sequences related to primorial base</a>.

%o (PARI)

%o A351566(n) = { my(p=2, c=0); while(n, if((n%p)>0, c++; if(2==c, return(p))); n = n\p; p = nextprime(1+p)); (1); };

%o A380536(n) = !(n%A351566(n));

%Y Characteristic function of A380537, whose complement A380538 gives the positions of 0's.

%Y Cf. A049345, A351566.

%K nonn,new

%O 1

%A _Antti Karttunen_, Feb 12 2025