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Search: id:A105346
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| A105346 |
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3-almost primes whose indices are 3-almost primes. |
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1
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| 42, 52, 76, 92, 116, 117, 125, 174, 182, 186, 212, 230, 266, 275, 282, 285, 316, 318, 325, 385, 406, 410, 423, 428, 436, 455, 470, 474, 507, 508, 534, 575, 604, 605, 618, 627, 654, 657, 670, 678, 682, 705, 710, 730, 754, 762, 772, 788, 834, 861, 903, 931
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The n-th 3-almost prime function applied to itself. This is the 3-almost prime equivalent of A091022, the latter being the n-th 2-almost prime function applied to itself. Note that this new iterated 3-almost prime sequence begins with the meaning of "Life, the Universe and Everything" and then generalizes to include the number of playing cards in a deck and the boiling point of water on the Fahrenheit scale.
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LINKS
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Eric Weisstein's World of Mathematics, Almost Prime.
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FORMULA
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a(n) = A014612(A014612(n)).
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EXAMPLE
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a(1) = 3-almost-prime(3-almost-prime(1)) = 3-almost-prime(8) = 42.
a(2) = 3-almost-prime(3-almost-prime(2)) = 3-almost-prime(12) = 52.
a(3) = 3-almost-prime(3-almost-prime(3)) = 3-almost-prime(18) = 76.
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MAPLE
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isA014612 := proc(n) option remember ; RETURN( numtheory[bigomega](n) = 3) ; end: A014612 := proc(n) option remember ; if n =1 then 8; else for a from procname(n-1)+1 do if isA014612(a) then RETURN(a) ; fi; od; fi; end: for n from 1 to 100 do q := A014612(A014612(n)) ; printf("%d, ", q) ; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 27 2009]
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CROSSREFS
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Cf. A014612, A000040, A001358, A007097, A091022, A105997, A105998, A101349, A106350.
Sequence in context: A095485 A124189 A063998 this_sequence A108119 A116262 A156394
Adjacent sequences: A105343 A105344 A105345 this_sequence A105347 A105348 A105349
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KEYWORD
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easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Apr 30 2005
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EXTENSIONS
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Extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 27 2009
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