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Search: id:A098146
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| A098146 |
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First odd semiprime > 10^n. |
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+0
2
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| 9, 15, 111, 1003, 10001, 100001, 1000001, 10000001, 100000001, 1000000013, 10000000003, 100000000007, 1000000000007, 10000000000015, 100000000000013, 1000000000000003, 10000000000000003, 100000000000000015
(list; graph; listen)
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OFFSET
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0,1
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LINKS
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Dario Alpern, Factorization using the Elliptic Curve Method.
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EXAMPLE
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a(0)=9 because 9=3*3 is the first odd semiprime following 10^0=1, a(13)=10000000000015=5*2000000000003.
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PROGRAM
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(PARI) print1(9, ", "); for(n=1, 10, forstep(i=10^n+1, 10^(n+1)-1, 2, f=factor(i); ms=matsize(f); if((ms[1]==1&&f[1, 2]==2)||(ms[1]==2&&f[1, 2]==1&&f[2, 2]==1), print1(i, ", "); break))) - Herman Jamke (hermanjamke(AT)fastmail.fm), Oct 21 2006
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CROSSREFS
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Cf. A046315 odd semiprimes, A098147(n)=a(n)-10^n continuation of this sequence, A003717 smallest n-digit prime.
Sequence in context: A029712 A136353 A136354 this_sequence A124274 A075134 A158789
Adjacent sequences: A098143 A098144 A098145 this_sequence A098147 A098148 A098149
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KEYWORD
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nonn
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AUTHOR
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Hugo Pfoertner (hugo(AT)pfoertner.org), Aug 28 2004
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