|
| |
|
|
A137510
|
|
Irregular triangle read by rows in which row n lists the divisors of n in the range 1 < d < n; or 0 if there are no such divisors.
|
|
3
|
|
|
|
0, 0, 0, 2, 0, 2, 3, 0, 2, 4, 3, 2, 5, 0, 2, 3, 4, 6, 0, 2, 7, 3, 5, 2, 4, 8, 0, 2, 3, 6, 9, 0, 2, 4, 5, 10, 3, 7, 2, 11, 0, 2, 3, 4, 6, 8, 12, 5, 2, 13, 3, 9, 2, 4, 7, 14, 0, 2, 3, 5, 6, 10, 15, 0, 2, 4, 8, 16, 3, 11, 2, 17, 5, 7, 2, 3, 4, 6, 9, 12, 18, 0, 2, 19, 3, 13, 2, 4, 5, 8, 10, 20, 0, 2, 3, 6, 7
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,4
|
|
|
COMMENTS
|
The length of row n is A264440(n). - Wolfdieter Lang, Jan 16 2016
Row n lists the nontrivial divisors of n, or 0 if there are no such divisors. - Omar E. Pol, Nov 22 2010
|
|
|
LINKS
|
Table of n, a(n) for n=1..97.
|
|
|
EXAMPLE
|
From Omar E. Pol, Nov 22 2010: (Start)
The irregular triangle begins:
0;
0;
0;
2;
0;
2, 3;
0;
2, 4;
3;
2, 5;
0,
2, 3, 4, 6;
(End)
|
|
|
MAPLE
|
for n from 1 to 80 do if isprime(n) or n = 1 then printf("0, ") ; else dvs := sort(convert(numtheory[divisors](n) minus {1, n}, list) ) ; for d in dvs do printf("%d, ", d) ; od: fi ; od: # R. J. Mathar, May 23 2008
with(numtheory): A:=proc (n) local div: div:=divisors(n): `minus`(div, {div[tau(n)], div[1]}) end proc: for n to 35 do A(n) end do: a:=proc (n) if A(n)={} then 0 else seq(A(n)[j], j=1..tau(n)-2) end if end proc: for n to 35 do a(n) end do; # yields sequence in triangular form - Emeric Deutsch, May 25 2008
|
|
|
MATHEMATICA
|
Array[Complement[Divisors@ #, {1, #}] &, {42}] /. {} -> {0} // Flatten (* Michael De Vlieger, Jan 16 2016 *)
|
|
|
CROSSREFS
|
Cf. A070824, A027750, A027751, A264440 (row length). Row sums give A048050.
Sequence in context: A299761 A141099 A127710 * A247303 A067871 A198632
Adjacent sequences: A137507 A137508 A137509 * A137511 A137512 A137513
|
|
|
KEYWORD
|
nonn,tabf,easy
|
|
|
AUTHOR
|
N. J. A. Sloane, May 08 2008
|
|
|
EXTENSIONS
|
More terms from R. J. Mathar and Emeric Deutsch, May 23 2008
|
|
|
STATUS
|
approved
|
| |
|
|
