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Search: id:A106708
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| A106708 |
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Replace n by the concatenation of its proper divisors (a(n) = 0 unless n is composite). |
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+0
6
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| 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; listen)
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OFFSET
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1,4
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LINKS
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Klaus Brockhaus, Table of n, a(n) for n=1..5000
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FORMULA
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a(n) = A037279(n)*A010051(n). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 01 2007
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MAPLE
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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 (mathar(AT)strw.leidenuniv.nl), Aug 01 2007
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PROGRAM
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(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 */
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CROSSREFS
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Cf. A037278, A120712, A037279, A131983 (records), A131984 (where records occur).
Sequence in context: A139003 A156438 A009378 this_sequence A138551 A133490 A051728
Adjacent sequences: A106705 A106706 A106707 this_sequence A106709 A106710 A106711
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KEYWORD
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nonn,base
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com), Jul 20 2007
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl) and Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Aug 01 2007
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