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 A322583 a(n) is the number of factorizations of n into factorial numbers larger than one; a(1) = 1. 8

%I

%S 1,1,0,1,0,1,0,1,0,0,0,1,0,0,0,1,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,1,0,0,

%T 0,1,0,0,0,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,

%U 0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1

%N a(n) is the number of factorizations of n into factorial numbers larger than one; a(1) = 1.

%C Values 1..7 occur for the first time at n = 1, 24, 576, 13824, 69120, 414720, 1658880.

%C In range 1..69120 differs from A034876 only at positions n = 1, 2, 9, 10 and 16.

%H Antti Karttunen, <a href="/A322583/b322583.txt">Table of n, a(n) for n = 1..69120</a>

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

%F a(24^n) = a(A009968(n)) = n+1.

%e a(4) = 1 because 4 = 2! * 2!.

%e a(24) = 2 because 24 = 4! = 3! * 2! * 2!.

%e a(576) = 3 because 576 = 4! * 4! = 4! * 3! * 2! * 2! = (3!)^2 * (2!)^4.

%e a(13824) = 4 because 13824 = (4!)^3 = (4!)^2 * 3! * (2!)^2 = 4! * (3!)^2 * (2!)^4 = (3!)^3 * (2!)^6.

%e a(69120) = 5 because 69120 = 6! * 4! * 2! * 2! = 6! * 3! * 2! * 2! * 2! * 2! = 5! * 3! * 3! * 2! * 2! * 2! * 2! = 5! * 4! * 4! = 5! * 4! * 3! * 2! * 2!. Note that 69120 < 24^4 = 331776.

%o (PARI) A322583(n, m=n) = if(1==n, 1, my(s=0); for(i=2, oo, my(f=i!); if(f>m, return(s)); if(!(n%f), s += A322583(n/f, f))));

%o (PARI)

%o A034968(n) = { my(s=0, b=2, d); while(n, d = (n%b); s += d; n = (n-d)/b; b++); (s); };

%o A322583(n, m=n) = if(1==n, 1, my(s=0); fordiv(n, d, if((d>1)&&(d<=m)&&(1==A034968(d)), s += A322583(n/d, d))); (s));

%Y Cf. A000142, A001013 (positions of nonzero terms), A009968, A034876, A034968.

%K nonn

%O 1,24

%A _Antti Karttunen_, Dec 25 2018

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Last modified September 21 13:37 EDT 2019. Contains 327253 sequences. (Running on oeis4.)