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A333262
Number of steps to reach 1 by iterating the alternating sum of divisors function A071324 starting from n.
3
0, 1, 2, 3, 4, 4, 5, 5, 6, 5, 6, 6, 7, 6, 7, 7, 8, 8, 9, 7, 8, 7, 8, 8, 9, 7, 8, 9, 10, 8, 9, 9, 9, 9, 10, 10, 11, 8, 10, 9, 10, 10, 11, 9, 11, 9, 10, 10, 12, 10, 11, 11, 12, 10, 11, 9, 10, 9, 10, 10, 11, 10, 10, 12, 10, 11, 12, 11, 11, 11, 12, 13, 14, 9, 11, 11
OFFSET
1,3
LINKS
FORMULA
a(n) = 0 if n = 1 and a(n) = a(A071324(n)) + 1 otherwise.
EXAMPLE
a(3) = 2 since it takes 2 iterations of A071324 to reach from 3 to 1: 3 -> 2 -> 1.
MATHEMATICA
f[n_] := Plus @@ (-(d = Divisors[n])*(-1)^(Range[Length[d], 1, -1])); a[n_] := Length @ FixedPointList[f, n] - 2; Array[a, 100]
CROSSREFS
Sequence in context: A360746 A374066 A056791 * A218767 A334863 A329202
KEYWORD
nonn
AUTHOR
Amiram Eldar, Mar 13 2020
STATUS
approved