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Search: id:A120383
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| A120383 |
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A number n is included if it satisfies: m divides n for all m's where the m-th prime divides n. |
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+0
1
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| 2, 4, 6, 8, 12, 16, 18, 24, 28, 30, 32, 36, 48, 54, 56, 60, 64, 72, 78, 84, 90, 96, 108, 112, 120, 128, 144, 150, 152, 156, 162, 168, 180, 192, 196, 216, 224, 234, 240, 252, 256, 270, 288, 300, 304, 312, 324, 330, 336, 360, 384, 390, 392, 414, 420, 432, 444, 448
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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28 = 2^2 *7. 2 is the first prime, 7 is the 4th prime. Since 1 and 4 both divide 28, then 28 is included in the sequence.
78 = 2*3*13. 2 is the first prime, 3 is the 2nd prime and 13 is the 6th prime. Since 1 and 2 and 6 each divide 78, then 78 is in the sequence. (Note that (1*2*6) does not divide 78.)
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MAPLE
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A000040inv := proc(n) local i; i:=1 ; while true do if ithprime(i) = n then RETURN(i) ; fi ; i := i+1 ; end ; end: isA120383 := proc(n) local pl, p, i, j ; pl := ifactors(n) ; pl := pl[2] ; for i from 1 to nops(pl) do p := pl[i] ; j := A000040inv(p[1]) ; if n mod j <> 0 then RETURN(false) ; fi ; od ; RETURN(true) ; end: for n from 2 to 800 do if isA120383(n) then printf("%d, ", n); fi ; od ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 02 2006
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CROSSREFS
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Sequence in context: A060765 A140110 A128397 this_sequence A055932 A140067 A067946
Adjacent sequences: A120380 A120381 A120382 this_sequence A120384 A120385 A120386
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Jun 29 2006
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 02 2006
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