A106708 a(n) is the concatenation of its nontrivial divisors.
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
Offset: 1
Links
- Klaus Brockhaus, Table of n, a(n) for n=1..5000
Crossrefs
Programs
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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
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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
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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 *) -
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 */ -
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
Formula
Extensions
More terms from R. J. Mathar and Klaus Brockhaus, Aug 01 2007
Name edited by Michael S. Branicky, Dec 31 2020