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A375478
Irregular triangle read by rows in which row n lists the iterates of the phi(x) map from n to 1, where phi(x) is Euler's totient function (A000010).
4
1, 2, 1, 3, 2, 1, 4, 2, 1, 5, 4, 2, 1, 6, 2, 1, 7, 6, 2, 1, 8, 4, 2, 1, 9, 6, 2, 1, 10, 4, 2, 1, 11, 10, 4, 2, 1, 12, 4, 2, 1, 13, 12, 4, 2, 1, 14, 6, 2, 1, 15, 8, 4, 2, 1, 16, 8, 4, 2, 1, 17, 16, 8, 4, 2, 1, 18, 6, 2, 1, 19, 18, 6, 2, 1, 20, 8, 4, 2, 1, 21, 12, 4, 2, 1
OFFSET
1,2
COMMENTS
First differs from A246700 at n = 22.
LINKS
FORMULA
T(n,1) = n; T(n,k) = A000010(T(n,k-1)), for k = 2..A049108(n).
EXAMPLE
Triangle begins:
1;
2, 1;
3, 2, 1;
4, 2, 1;
5, 4, 2, 1;
6, 2, 1;
7, 6, 2, 1;
8, 4, 2, 1;
9, 6, 2, 1;
10, 4, 2, 1;
...
MATHEMATICA
Array[Most[FixedPointList[EulerPhi, #]] &, 25]
CROSSREFS
Supersequence of A246700.
Cf. A000010, A049108 (row lengths), A053478 (row sums).
Sequence in context: A361101 A308780 A246700 * A073932 A082404 A334725
KEYWORD
nonn,tabf,easy
AUTHOR
Paolo Xausa, Aug 17 2024
STATUS
approved