A345940 - OEIS

%I #12 Jul 04 2021 22:05:35

%S 0,0,0,2,0,0,0,2,6,0,0,6,0,0,0,2,0,6,0,0,0,0,0,6,20,0,6,0,0,0,0,2,0,0,

%T 0,6,0,0,0,0,0,0,0,0,30,0,0,6,42,20,0,0,0,6,0,0,0,0,0,0,0,0,0,2,0,0,0,

%U 0,0,0,0,6,0,0,45,0,0,0,0,40,6,0,0,0,0,0,0,0,0,30,0,0,0,0,0,6,0,42,0,20

%N Factorial of the largest prime factor of n, read modulo n: a(n) = A006530(n)! mod n.

%H Antti Karttunen, <a href="/A345940/b345940.txt">Table of n, a(n) for n = 1..65537</a>

%H <a href="/index/Fa#factorial">Index entries for sequences related to factorial numbers</a>

%F a(n) = A000142(A006530(n)) modulo n.

%t Table[Mod[First@Last@FactorInteger[n]!,n],{n,100}] (* _Giorgos Kalogeropoulos_, Jul 04 2021 *)

%o (PARI)

%o A006530(n) = if(1==n, n, my(f=factor(n)); f[#f~, 1]);

%o A345940(n) = ((A006530(n)!)%n);

%Y Cf. A000142, A006530, A057109 (positions of nonzero terms), A345951.

%K nonn,look

%O 1,4

%A _Antti Karttunen_, Jul 04 2021