|
Search: id:A137510
|
|
|
| A137510 |
|
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. |
|
+0
1
|
|
| 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; listen)
|
|
|
OFFSET
|
1,4
|
|
|
COMMENT
|
a(n) = 0 if n is 1 or a prime.
|
|
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 (mathar(AT)strw.leidenuniv.nl), 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 (deutsch(AT)duke.poly.edu), May 25 2008
|
|
CROSSREFS
|
Cf. A070824, A027750, A027751.
Sequence in context: A111565 A141099 A127710 this_sequence A067871 A060155 A127954
Adjacent sequences: A137507 A137508 A137509 this_sequence A137511 A137512 A137513
|
|
KEYWORD
|
nonn,tabf,easy
|
|
AUTHOR
|
njas, May 08 2008
|
|
EXTENSIONS
|
More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl) and Emeric Deutsch (deutsch(AT)duke.poly.edu), May 23 2008
|
|
|
Search completed in 0.002 seconds
|
