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A096098
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a(1) = 2, a(2) = 1; for n >= 3, a(n) = least number not included earlier that divides the concatenation of all previous terms.
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1
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2, 1, 3, 71, 7, 21, 599, 173, 11, 23, 161, 49, 13, 9, 131, 19, 33, 17, 1489, 331, 3989, 69, 3097350956401900335673788279883089441874368101, 349387, 5651, 443, 29, 51, 479470832244949, 661, 1129, 1873, 181, 1544577973887516219070997863, 521
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Conjecture:(1) Every concatenation is squarefree. (2) This is a rearrangement of the squarefree numbers not divisible by 5.
The concatenations are not always squarefree, since a(12)=49 and a(14)=9. There are no more even numbers in the sequence since odd a(n) => odd concatenation => odd a(n+1). Conjecture:(3) the sequence for n>=2 is a permutation of the positive integers not divisible by 2 or 5. a(29) is probably 479470832244949, in which case the sequence continues 479470832244949, 661, 1129, 1873, 181. - Martin Fuller (martin_n_fuller(AT)btinternet.com), Nov 21 2007
Factorization for a(29): 479470832244949*3*17*43217123024009614997922599713504735424547343*P51 [From Sean A. Irvine (sairvin(AT)xtra.co.nz), May 25 2010]
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EXAMPLE
| a(6) = 21 as 213717 = 3*7*10177.
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CROSSREFS
| Cf. A096097.
Sequence in context: A059333 A106485 A126008 * A096097 A016585 A143316
Adjacent sequences: A096095 A096096 A096097 * A096099 A096100 A096101
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KEYWORD
| base,nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jun 24 2004
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EXTENSIONS
| More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 03 2007
a(23)-a(26) from N. J. A. Sloane (njas(AT)research.att.com), Nov 10 2007
Corrected and extended by Martin Fuller (martin_n_fuller(AT)btinternet.com), Nov 21 2007
More terms from Sean A. Irvine (sairvin(AT)xtra.co.nz), May 25 2010
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