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A154367
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Numbers n such that sum of prime factors of composite(n) = prime and smallest prime factor composite(n) + largest prime factor of composite(n) = composite.
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0
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18, 30, 36, 39, 44, 53, 54, 73, 76, 86, 112, 113, 116, 126, 132, 134, 141, 160, 163, 175, 191, 194, 197, 211, 214, 219, 231, 233, 250, 258, 265, 276, 279, 294, 295, 301, 308, 311, 312, 320, 325, 331, 333, 335, 338, 340, 341, 350, 351, 361, 376, 383, 385, 394
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| If composite(k=18)=28=2*2*7, 2+2+7=13(prime) and 2+7=9(composite), then 18=a(1). If composite(k=30)=45=3*3*5, 3+3+5=11(prime) and 3+5=8(composite), then 30=a(2), etc.
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MAPLE
| Contribution from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 05 2010: (Start)
isA002808 := proc(n) n >= 4 and not isprime(n) ; end proc:
A046343 := proc(n) pss(A002808(n)) ; end proc:
A020639 := proc(n) numtheory[factorset](n) ; min(op(%)) ; end proc:
A006530 := proc(n) numtheory[factorset](n) ; max(op(%)) ; end proc:
for n from 1 to 500 do if isprime(A046343(n)) and isA002808( A020639(A002808(n)) + A006530(A002808(n)) ) then printf("%d, ", n) ; end if; end do: (End)
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CROSSREFS
| Cf. Primes in A000040. Composites in A002808.
Sequence in context: A144833 A032612 A151700 * A161164 A092357 A141115
Adjacent sequences: A154364 A154365 A154366 * A154368 A154369 A154370
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KEYWORD
| nonn
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AUTHOR
| Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jan 08 2009
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EXTENSIONS
| Corrected (44 inserted, 120 removed, 146 removed) and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 05 2010
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