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A136181 Irregular array read by rows: row n contains the LCMs of each pair of consecutive positive divisors of n. 5
2, 3, 2, 4, 5, 2, 6, 6, 7, 2, 4, 8, 3, 9, 2, 10, 10, 11, 2, 6, 12, 12, 12, 13, 2, 14, 14, 3, 15, 15, 2, 4, 8, 16, 17, 2, 6, 6, 18, 18, 19, 2, 4, 20, 10, 20, 3, 21, 21, 2, 22, 22, 23, 2, 6, 12, 12, 24, 24, 24, 5, 25, 2, 26, 26, 3, 9, 27, 2, 4, 28, 14, 28, 29, 2, 6, 15, 30, 30, 30, 30, 31, 2, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

Each row has d(n)-1 terms, where d(n) is the number of positive divisors of n. The first row listed is row 2.

LINKS

Diana Mecum, Table of n, a(n) for n = 2..6070

EXAMPLE

The positive divisors of 20 are 1,2,4,5,10,20; lcm(1,2)=2, lcm(2,4)=4, lcm(4,5)=20, lcm(5,10)=10, and lcm(10,20)=20, so row 20 is (2,4,20,10,20).

Irregular array begins:

  2;

  3;

  2, 4;

  5;

  2, 6, 6;

  7;

  2, 4, 8;

  3, 9;

  2, 10, 10;

11;

  2, 6, 12, 12, 12;

...

MATHEMATICA

Flatten[Table[LCM@@@(Partition[Divisors[n], 2, 1]), {n, 2, 35}]]  (* Harvey P. Dale, Apr 22 2011 *)

PROG

(PARI) tabf(nn) = {for (n=2, nn, d = divisors(n); for (k=2, #d, print1(lcm(d[k-1], d[k]), ", "); ); print; ); } \\ Michel Marcus, Mar 13 2018

CROSSREFS

Cf. A027750, A136178, A136182, A136183.

Sequence in context: A214540 A214595 A029638 * A265110 A304742 A003976

Adjacent sequences:  A136178 A136179 A136180 * A136182 A136183 A136184

KEYWORD

nonn,tabf

AUTHOR

Leroy Quet, Dec 19 2007

EXTENSIONS

a(24)-a(85) from Diana L. Mecum, Dec 29 2008

STATUS

approved

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Last modified November 21 03:01 EST 2018. Contains 317427 sequences. (Running on oeis4.)