A255242 Calculate the aliquot parts of a number n and take their sum. Then repeat the process calculating the aliquot parts of all the previous aliquot parts and add their sum to the previous one. Repeat the process until the sum to be added is zero. Sequence lists these sums.

0, 1, 1, 4, 1, 8, 1, 12, 5, 10, 1, 30, 1, 12, 11, 32, 1, 36, 1, 38, 13, 16, 1, 92, 7, 18, 19, 46, 1, 74, 1, 80, 17, 22, 15, 140, 1, 24, 19, 116, 1, 90, 1, 62, 51, 28, 1, 256, 9, 62, 23, 70, 1, 136, 19, 140, 25, 34, 1, 286, 1, 36, 61, 192, 21, 122, 1, 86, 29, 114

Offset

1,4

Comments

a(n) = 1 if n is prime.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Paolo P. Lava)

Formula

a(1) = 0.

a(2^k) = k*2^(k-1) = A001787(k), for k>=1.

a(n^k) = (n^k-2^k))/(n-2), for n odd prime and k>=1.

In particular:

a(3^k) = A001047(k-1);

a(5^k) = A016127(k-1);

a(7^k) = A016130(k-1);

a(11^k) = A016135(k-1).

Example

The aliquot parts of 8 are 1, 2, 4 and their sum is 7.
Now, let us calculate the aliquot parts of 1, 2 and 4:
1 => 0;  2 => 1;  4 => 1, 2.  Their sum is 0 + 1 + 1 + 2 = 4.
Let us calculate the aliquot parts of 1, 1, 2:
1 => 0;  1 = > 0; 2 => 1. Their sum is 1.
We have left 1: 1 => 0.
Finally, 7 + 4 + 1 = 12. Therefore a(8) = 12.

Maple

with(numtheory): P:=proc(q) local a, b, c, k, n, t, v;
for n from 1 to q do b:=0; a:=sort([op(divisors(n))]); t:=nops(a)-1;
while add(a[k], k=1..t)>0 do b:=b+add(a[k], k=1..t); v:=[];
for k from 2 to t do c:=sort([op(divisors(a[k]))]); v:=[op(v), op(c[1..nops(c)-1])]; od;
a:=v; t:=nops(a); od; print(b); od; end: P(10^3);

Mathematica

f[s_] := Flatten[Most[Divisors[#]] & /@ s]; a[n_] := Total@Flatten[FixedPointList[ f, {n}]] - n; Array[a, 100] (* Amiram Eldar, Apr 06 2019 *)

Prog

(PARI) ali(n) = setminus(divisors(n), Set(n));
a(n) = my(list = List(), v = [n]); while (#v, my(w = []); for (i=1, #v, my(s=ali(v[i])); for (j=1, #s, w = concat(w, s[j]); listput(list, s[j])); ); v = w; ); vecsum(Vec(list)); \\ Michel Marcus, Jul 15 2023

Crossrefs

Cf. A001047, A001065, A001787, A006516, A016127, A016130, A016135, A255243.

Sequence in context: A158496 A265722 A019425 * A329371 A305834 A295786

Adjacent sequences: A255239 A255240 A255241 * A255243 A255244 A255245

Keyword

nonn

Author

Paolo P. Lava, Feb 19 2015

Status

approved