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 A163838 a(n) = (n-th composite) * (number of nontrivial divisors of n-th composite). 1
 4, 12, 16, 9, 20, 48, 28, 30, 48, 72, 80, 42, 44, 144, 25, 52, 54, 112, 180, 128, 66, 68, 70, 252, 76, 78, 240, 252, 176, 180, 92, 384, 49, 200, 102, 208, 324, 110, 336, 114, 116, 600, 124, 252, 320, 130, 396, 272, 138, 420, 720, 148, 300, 304, 154, 468, 640, 243 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The trivial divisors of the n-th composite are 1 and the n-th composite. LINKS FORMULA a(n) = A002808(n)*A144925(n). EXAMPLE a(1) =  4 (= 4*1); a(2) = 12 (= 6*2); a(3) = 16 (= 8*2); a(4) =  9 (= 9*1); a(5) = 20 (= 10*2); a(6) = 48 (= 12*4). MAPLE A002808 := proc(n) option remember; local a; 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: A070824 := proc(n) numtheory[tau](n)-2 ; end: A144925 := proc(n) A070824(A002808(n)) ; end: A163838 := proc(n) A144925(n)*A002808(n) ; end: seq(A163838(n), n=1..80) ; # R. J. Mathar, Oct 10 2009 CROSSREFS Cf. A002808, A070824, A144925. Sequence in context: A224785 A195547 A335528 * A228091 A157849 A137257 Adjacent sequences:  A163835 A163836 A163837 * A163839 A163840 A163841 KEYWORD nonn AUTHOR Juri-Stepan Gerasimov, Aug 05 2009, Aug 06 2009 EXTENSIONS 56 replaced with 112, 310 replaced with 320, and 468 inserted by R. J. Mathar, Oct 10 2009 STATUS approved

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Last modified September 27 22:36 EDT 2020. Contains 337388 sequences. (Running on oeis4.)