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A145351
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Composites of the form : smallest prime factor of composite(n)+largest prime factor of composite(n)=prime and n=prime.
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1
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6, 10, 20, 22, 30, 44, 54, 58, 66, 82, 96, 108, 120, 136, 142, 144, 204, 232, 324, 330, 340, 352, 384, 464, 492, 544, 596, 616, 704, 738, 750, 792, 870, 894, 918, 960, 990, 1062, 1234, 1312, 1318, 1326, 1498, 1534, 1540, 1566, 1576, 1632, 1694, 1700, 1722
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| If 6(composite(n=2(prime)))=2*3 and 2+3=5(prime), then 6=a(1). If 10(composite(n=5(prime)))=2*5 and 2+5=7(prime), then 10=a(2). If 22(composite(n=13(prime)))=2*13 and 2+13(prime), then 22=a(3). If 44(composite(n=29(prime)))=2*2*11 and 2+2+11(prime), then 44=a(4), etc.
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MAPLE
| Contribution from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 01 2010: (Start)
A020639 := proc(n) numtheory[factorset](n) ; min(op(%)) ; end proc:
A006530 := proc(n) numtheory[factorset](n) ; max(op(%)) ; end proc:
A002808 := proc(n) if n = 1 then 4; else for a from procname(n-1)+1 do if not isprime(a) then return a; end if; end do: end if; end proc:
A065858 := proc(n) A002808(ithprime(n)) ; end proc:
A145351 := proc(n) c := A065858(n) ; if isprime(A020639(c) + A006530(c)) then printf("%d, ", c) ; end if; end proc:
seq(A145351(n), n=1..400) ; (End)
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CROSSREFS
| Cf. A000040, A002808.
Sequence in context: A138828 A109312 A095985 * A015783 A068017 A169810
Adjacent sequences: A145348 A145349 A145350 * A145352 A145353 A145354
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KEYWORD
| nonn
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AUTHOR
| Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jan 04 2009
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EXTENSIONS
| Corrected (inserted 20 from n=5, 30 from n=8, removed 200) and extended beyond 204 by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 01 2010
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