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A278028 Let {c(i)} = A007916 denote the sequence of numbers > 1 which are not perfect powers. Every positive integer n has a unique representation as a tower n = c(x_1)^c(x_2)^c(x_3)^...^c(x_k), where the exponents are nested from the right. The sequence is an irregular triangle read by rows, where the n-th row lists x_1, ..., x_k. 15
1, 2, 1, 1, 3, 4, 5, 1, 2, 2, 1, 6, 7, 8, 9, 10, 11, 1, 1, 1, 12, 13, 14, 15, 16, 17, 18, 19, 3, 1, 20, 2, 2, 21, 22, 23, 24, 1, 3, 25, 26, 27, 4, 1, 28, 29, 30, 31 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Row lengths are A288636(n). - Gus Wiseman, Jun 12 2017

LINKS

N. J. A. Sloane, Table of n, a(n) for n = 1..20181

N. J. A. Sloane, Maple programs for A007916, A278028, A278029, A052409, A089723, A277564

EXAMPLE

Rows 2 through 32 are:

1,

2,

1, 1,

3,

4,

5,

1, 2,

2, 1,

6,

7,

8,

9,

10,

11,

1, 1, 1,

12,

13,

14,

15,

16,

17,

18,

19,

3, 1,

20,

2, 2,

21,

22,

23,

24,

1, 3,

...

CROSSREFS

See A277564 for another version.

Cf. A007916, A089723, A277562, A288636.

Sequence in context: A307277 A210691 A262175 * A124424 A057044 A153899

Adjacent sequences:  A278025 A278026 A278027 * A278029 A278030 A278031

KEYWORD

nonn,tabf

AUTHOR

N. J. A. Sloane, Nov 09 2016

STATUS

approved

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Last modified April 18 14:58 EDT 2021. Contains 343089 sequences. (Running on oeis4.)