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A290600 Irregular triangle T(n, k) read by rows: positive numbers non-coprime to A002808(n) and smaller than A002808(n), sorted increasingly. 3
2, 2, 3, 4, 2, 4, 6, 3, 6, 2, 4, 5, 6, 8, 2, 3, 4, 6, 8, 9, 10, 2, 4, 6, 7, 8, 10, 12, 3, 5, 6, 9, 10, 12, 2, 4, 6, 8, 10, 12, 14, 2, 3, 4, 6, 8, 9, 10, 12, 14, 15, 16, 2, 4, 5, 6, 8, 10, 12, 14, 15, 16, 18, 3, 6, 7, 9, 12, 14, 15, 18 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The length of row n is A290599(n).

Row n gives the complement of row A038566(A002808(n), k) with respect to [1, 2, ..., A002808(n) - 1].

LINKS

Table of n, a(n) for n=1..71.

FORMULA

T(n, k) = k-th entry in the list of increasingly sorted numbers of the set {m = 1..A002808(n)-1: gcd(n, m) not equal to 1}.

EXAMPLE

The irregular triangle T(n, k) begins (N(n) = A002808(n)):

n   N(n) \ k  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 ...

1   4         2

2   6         2  3  4

3   8         2  4  6

4   9         3  6

5   10        2  4  5  6  8

6   12        2  3  4  6  8  9 10

7   14        2  4  6  7  8 10 12

8   15        3  5  6  9 10 12

9   16        2  4  6  8 10 12 14

10  18        2  3  4  6  8  9 10 12 14 15 16

11  20        2  4  5  6  8 10 12 14 15 16 18

12  21        3  6  7  9 12 14 15 18

13  22        2  4  6  8 10 11 12 14 16 18 20

14  24        2  3  4  6  8  9 10 12 14 15 16 18 20 21 22

15  25        5 10 15 20

...

MATHEMATICA

Table[With[{c = FixedPoint[n + PrimePi@ #] + 1 &, n + PrimePi@ n + 1]}, Select[Range[c - 1], ! CoprimeQ[#, c] &]], {n, 12}] // Flatten (* Michael De Vlieger, Sep 03 2017 *)

CROSSREFS

Cf. A002808, A038566, A290599, A290601, A290602.

Sequence in context: A238958 A238971 A194331 * A143595 A211702 A208521

Adjacent sequences:  A290597 A290598 A290599 * A290601 A290602 A290603

KEYWORD

nonn,tabf

AUTHOR

Wolfdieter Lang, Aug 30 2017

STATUS

approved

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Last modified July 22 11:00 EDT 2019. Contains 325219 sequences. (Running on oeis4.)