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Search: id:A123386
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| A123386 |
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Largest difference between successive semiprimes up to 10^n inclusive. |
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+0
1
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OFFSET
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1,1
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COMMENT
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There are 4 semiprimes up to 10^1 {4, 6, 9, 10}. The differences between successive semiprimes are {2, 3, 1}. Thus a(1) = Max[ {2, 3, 1} ] = 3.
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PROGRAM
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(PARI) A001358(prev)={ local(a=prev+1) ; while(bigomega(a)!=2, a++ ; ) ; return(a) ; } A123386(n)={ local(sp1=4, sp2=6, a=2) ; while(sp2<=10^n, a=max(a, sp2-sp1) ; sp1=sp2 ; sp2=A001358(sp1) ; ) ; return(a) ; } { for(n=1, 13, print(A123386(n)) ; ) ; } - 2 more term from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 17 2008
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CROSSREFS
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Cf. A001358, A065516, A036352, A038460, A053303.
Sequence in context: A004232 A140462 A093523 this_sequence A060999 A089187 A004006
Adjacent sequences: A123383 A123384 A123385 this_sequence A123387 A123388 A123389
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KEYWORD
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hard,more,nonn
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AUTHOR
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Alexander Adamchuk (alex(AT)kolmogorov.com), Nov 09 2006
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EXTENSIONS
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2 more term from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 17 2008
a(8)-a(9) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Sep 05 2008
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