|
| |
|
|
A106708
|
|
a(n) is the concatenation of its nontrivial divisors.
|
|
10
|
|
|
|
0, 0, 0, 2, 0, 23, 0, 24, 3, 25, 0, 2346, 0, 27, 35, 248, 0, 2369, 0, 24510, 37, 211, 0, 2346812, 5, 213, 39, 24714, 0, 23561015, 0, 24816, 311, 217, 57, 234691218, 0, 219, 313, 24581020, 0, 23671421, 0, 241122, 35915, 223, 0, 23468121624, 7, 251025, 317
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,4
|
|
|
LINKS
|
Klaus Brockhaus, Table of n, a(n) for n=1..5000
|
|
|
FORMULA
|
a(n) = A037279(n) * A010051(n). - R. J. Mathar, Aug 01 2007
|
|
|
MAPLE
|
A106708 := proc(n) local dvs ; if isprime(n) or n = 1 then 0; else dvs := [op(numtheory[divisors](n) minus {1, n} )] ; dvs := sort(dvs) ; cat(op(dvs)) ; fi ; end: seq(A106708(n), n=1..80) ; # R. J. Mathar, Aug 01 2007
|
|
|
MATHEMATICA
|
Table[If[CompositeQ[n], FromDigits[Flatten[IntegerDigits/@Rest[ Most[ Divisors[ n]]]]], 0], {n, 60}] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 22 2020 *)
|
|
|
PROG
|
(PARI) {map(n) = local(d); d=divisors(n); if(#d<3, 0, d[1]=""; eval(concat(vecextract(d, concat("..", #d-1)))))} for(n=1, 51, print1(map(n), ", ")) /* Klaus Brockhaus, Aug 05 2007 */
(Haskell)
a106708 1 = 0
a106708 n
| a010051 n == 1 = 0
| otherwise = read $ concat $ (map show) $ init $ tail $ a027750_row n
-- Reinhard Zumkeller, May 01 2012
(Python)
from sympy import divisors
def a(n):
nontrivial_divisors = [d for d in divisors(n)[1:-1]]
if len(nontrivial_divisors) == 0: return 0
else: return int("".join(str(d) for d in nontrivial_divisors))
print([a(n) for n in range(1, 52)]) # Michael S. Branicky, Dec 31 2020
|
|
|
CROSSREFS
|
Cf. A037278, A120712, A037279, A131983 (records), A131984 (where records occur).
Cf. A027750, A010051, A037285, A037277, A163870.
Sequence in context: A293938 A254042 A009378 * A138551 A133490 A051728
Adjacent sequences: A106705 A106706 A106707 * A106709 A106710 A106711
|
|
|
KEYWORD
|
nonn,base
|
|
|
AUTHOR
|
N. J. A. Sloane, Jul 20 2007
|
|
|
EXTENSIONS
|
More terms from R. J. Mathar and Klaus Brockhaus, Aug 01 2007
Name edited by Michael S. Branicky, Dec 31 2020
|
|
|
STATUS
|
approved
|
| |
|
|
