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A130846
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Replace n by the concatenation of its anti-divisors.
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3
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2, 3, 23, 4, 235, 35, 26, 347, 237, 58, 2359, 349, 2610, 311, 235711, 45712, 2313, 3813, 2614, 345915, 235915, 716, 2371017, 3417, 2561118, 3581119, 2319, 41220, 237921, 35791321, 2561322, 3423, 23101423, 824, 2351525, 3457111525, 2671126, 391627
(list; graph; refs; listen; history; internal format)
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OFFSET
| 3,1
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COMMENTS
| Number of anti-divisors concatenated to form a(n) is A066272(n). We may consider prime values of the concatenated anti-divisor sequence and we may iterate it, i.e. n, a(n), a(a(n)), a(a(a(n))) which leads to questions of trajectory, cycles, fixed points.
See A066272 for definition of anti-divisor.
Primes in this sequence are at n=3,4,5,10,14,16,40,46,100,145,149,... - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 24 2007
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LINKS
| Jon Perry, The Anti-Divisor, cached copy.
J. V. Post, Factors of first 62 terms
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EXAMPLE
| 3: 2, so a(3) = 2.
4: 3, so a(4) = 3.
5: 2, 3, so a(5) = 23.
6: 4, so a(6) = 4.
7: 2, 3, 5, so a(7) = 235.
17: 2, 3, 5, 7, 11, so a(17) = 235711
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MAPLE
| antiDivs := proc(n) local resul, odd2n, r ; resul := {} ; for r in ( numtheory[divisors](2*n-1) union numtheory[divisors](2*n+1) ) do if n mod r <> 0 and r> 1 and r < n then resul := resul union {r} ; fi ; od ; odd2n := numtheory[divisors](2*n) ; for r in odd2n do if ( r mod 2 = 1) and r > 2 then resul := resul union {2*n/r} ; fi ; od ; RETURN(resul) ; end: A130846 := proc(n) cat(op(antiDivs(n))) ; end: seq(A130846(n), n=3..80) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 24 2007
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CROSSREFS
| Cf. A037278, A066272, A120712, A106708, A130799.
Sequence in context: A046965 A119679 A191648 * A114101 A114007 A071819
Adjacent sequences: A130843 A130844 A130845 * A130847 A130848 A130849
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KEYWORD
| base,easy,nonn
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AUTHOR
| Jonathan Vos Post (jvospost3(AT)gmail.com), Jul 20 2007, Jul 22 2007
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EXTENSIONS
| More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 24 2007
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