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A053477
Sum of iterates of divisor number function A000005.
2
1, 2, 5, 9, 7, 15, 9, 17, 14, 19, 13, 27, 15, 23, 24, 23, 19, 33, 21, 35, 30, 31, 25, 41, 30, 35, 36, 43, 31, 47, 33, 47, 42, 43, 44, 50, 39, 47, 48, 57, 43, 59, 45, 59, 60, 55, 49, 67, 54, 65, 60, 67, 55, 71, 64, 73, 66, 67, 61, 87, 63, 71, 78, 73, 74, 83, 69, 83, 78, 87, 73
OFFSET
1,2
LINKS
EXAMPLE
If n is prime then the iteration sequence is {p,2} and the sum is p+2. If n=30, then iterations of the d function are {30,8,4,3,2} and their sum is a(30)=47.
MAPLE
f:= proc(n) option remember;
if n <= 2 then n
else n + procname(numtheory:-tau(n));
fi
end proc:
map(f, [$1..80]); # Robert Israel, Nov 14 2016
MATHEMATICA
g[n_] := DivisorSigma[0, n]; f[n_] := Plus @@ Drop[ FixedPointList[g, n], -1]; Table[ f[n], {n, 71}] (* Robert G. Wilson v, Dec 16 2004 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Jan 14 2000
STATUS
approved