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A306884 Sum over all partitions of n of the power tower evaluation x^y^...^z, where x, y, ..., z are the parts in (weakly) decreasing order. 5
1, 1, 3, 6, 14, 28, 93, 270, 86170, 7625640881546 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(10) = 200352993...611306920 has 19729 decimal digits.

LINKS

Table of n, a(n) for n=0..9.

Eric Weisstein's World of Mathematics, Power Tower

Wikipedia, Exponentiation

Wikipedia, Identity element

Wikipedia, Operator associativity

Wikipedia, Partition (number theory)

EXAMPLE

a(0) = 1 because the empty partition () has no parts, the exponentiation operator ^ is right-associative, and 1 is the right identity of exponentiation.

a(6) = 1^1^1^1^1^1 + 2^1^1^1^1 + 2^2^1^1 + 2^2^2 + 3^1^1^1 + 3^2^1 + 3^3 + 4^1^1 + 4^2 + 5^1 + 6 = 1 + 2 + 4 + 16 + 3 + 9 + 27 + 4 + 16 + 5 + 6 = 93.

MAPLE

f:= l-> `if`(l=[], 1, l[1]^f(subsop(1=(), l))):

a:= n-> add(f(sort(l, `>`)), l=combinat[partition](n)):

seq(a(n), n=0..9);

CROSSREFS

Cf. A006906, A066186, A306895, A306901, A306902, A306903, A306918.

Sequence in context: A200544 A308448 A055890 * A219768 A038359 A038360

Adjacent sequences:  A306881 A306882 A306883 * A306885 A306886 A306887

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Mar 15 2019

STATUS

approved

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Last modified January 23 07:07 EST 2020. Contains 331168 sequences. (Running on oeis4.)