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A106708 Replace n by the concatenation of its proper divisors (a(n) = 0 unless n is composite). 10

%I

%S 0,0,0,2,0,23,0,24,3,25,0,2346,0,27,35,248,0,2369,0,24510,37,211,0,

%T 2346812,5,213,39,24714,0,23561015,0,24816,311,217,57,234691218,0,219,

%U 313,24581020,0,23671421,0,241122,35915,223,0,23468121624,7,251025,317

%N Replace n by the concatenation of its proper divisors (a(n) = 0 unless n is composite).

%H Klaus Brockhaus, <a href="/A106708/b106708.txt">Table of n, a(n) for n=1..5000</a>

%F a(n) = A037279(n)*A010051(n). - _R. J. Mathar_, Aug 01 2007

%p 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

%o (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 */

%o (Haskell)

%o a106708 1 = 0

%o a106708 n

%o | a010051 n == 1 = 0

%o | otherwise = read $ concat $ (map show) $ init $ tail $ a027750_row n

%o -- _Reinhard Zumkeller_, May 01 2012

%Y Cf. A037278, A120712, A037279, A131983 (records), A131984 (where records occur).

%Y Cf. A027750, A010051, A037285, A037277.

%K nonn,base

%O 1,4

%A _N. J. A. Sloane_, Jul 20 2007

%E More terms from _R. J. Mathar_ and _Klaus Brockhaus_, Aug 01 2007

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Last modified December 21 18:52 EST 2014. Contains 252325 sequences.