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A037279 If n is composite, replace n with the concatenation of its proper divisors, otherwise a(n) = n. 6
1, 2, 3, 2, 5, 23, 7, 24, 3, 25, 11, 2346, 13, 27, 35, 248, 17, 2369, 19, 24510, 37, 211, 23, 2346812, 5, 213, 39, 24714, 29, 23561015, 31, 24816, 311, 217, 57, 234691218, 37, 219, 313, 24581020, 41, 23671421, 43, 241122, 35915, 223, 47, 23468121624, 7 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

Divisors of 12 are 1,2,3,4,6,12, so a(12)=2346.

MAPLE

A037279 := proc(n) local dvs ; if isprime(n) or n = 1 then n; else dvs := [op(numtheory[divisors](n) minus {1, n} )] ; dvs := sort(dvs) ; cat(op(dvs)) ; fi ; end: seq(A037279(n), n=1..80) ; # R. J. Mathar, Jul 23 2007

MATHEMATICA

f[n_]:=If[PrimeQ[n], n, FromDigits[Flatten[IntegerDigits/@Rest[ Most[ Divisors[n]]]]]]; Join[{1}, Array[f, 50, 2]] (* Harvey P. Dale, Sep 24 2012 *)

CROSSREFS

Cf. A037278, A120712, A106708.

Sequence in context: A120716 A084318 A084317 * A163591 A085307 A078599

Adjacent sequences:  A037276 A037277 A037278 * A037280 A037281 A037282

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane

EXTENSIONS

More terms from Erich Friedman

Edited by N. J. A. Sloane, Aug 29 2008 at the suggestion of R. J. Mathar

STATUS

approved

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Last modified December 12 22:57 EST 2018. Contains 318081 sequences. (Running on oeis4.)