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A090896 a(n) = sigma^n(n), where sigma^n denotes functional iteration. 2
1, 4, 8, 24, 120, 1170, 1512, 15748, 15748, 61440, 196584, 1572840, 1098240, 15605760, 50328576, 7074432, 355532800, 2143289344, 13815410400, 224319234048, 33541980160, 109760857440, 1468475386560, 33151875434496, 1415960985600, 1510712608204800 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(8) = a(9). Are there any other numbers m, n such that a(m) = a(n)? a(16) < a(15); a(25) < a(24). How often is a(n+1) < a(n)?

LINKS

Table of n, a(n) for n=1..26.

EXAMPLE

a(3) = sigma^3(3) = sigma^2(4) = sigma(7) = 8

MAPLE

a:= n-> (numtheory[sigma]@@n)(n):

seq(a(n), n=1..30);  # Alois P. Heinz, Oct 03 2018

CROSSREFS

Main diagonal of A129246.

Cf. A000203, A101303.

Sequence in context: A303989 A052578 A066631 * A131637 A163143 A154586

Adjacent sequences:  A090893 A090894 A090895 * A090897 A090898 A090899

KEYWORD

nonn

AUTHOR

Gabriel Cunningham (gcasey(AT)mit.edu), Feb 25 2004

STATUS

approved

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Last modified April 15 12:55 EDT 2021. Contains 342977 sequences. (Running on oeis4.)