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A160758
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Integer averages of first n nonprime numbers for some n.
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3
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1, 8, 25, 33, 359, 2948, 3291, 4959, 22350, 33357, 60907, 80962, 8276347, 11856980, 15254419, 176009996, 967538242, 1729774831, 9977169279, 193005936726
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| A variant of A050248 for nonprimes.
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FORMULA
| (1/n)*Sum {j=1..n} NonPrime_j is an integer. [From Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 05 2009]
a(n) = A164280(n) / A129749(n).
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EXAMPLE
| Sum of first 44 nonprimes is 1452. 1452 / 44 = 33, hence 33 is in the sequence,
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MATHEMATICA
| lst = {}; s = 0; c = 0; k = 1; While[k < 2700000000, If[ !PrimeQ@k, c++; s = s + k; If[Mod[s, c] == 0, AppendTo[lst, s/c]]]; k++ ]; lst [From Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 05 2009]
a=0; lst={}; Do[If[ !PrimeQ[n], m=n; a+=m; If[a/n==IntegerPart[a/n], AppendTo[lst, a/n]]], {n, 9!}]; lst
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PROG
| (MAGMA) S:=[]; a:=0; c:=0; for n in [1..40000000] do if not IsPrime(n) then a+:=n; c+:=1; if a mod c eq 0 then Append(~S, a div c); end if; end if; end for; S; [From Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Aug 11 2009]
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CROSSREFS
| Cf. A050248, integer averages of n primes for some n
Cf. A018252, A051349, A164280, A129749.
Sequence in context: A030796 A116086 A042611 * A015804 A161448 A031096
Adjacent sequences: A160755 A160756 A160757 * A160759 A160760 A160761
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KEYWORD
| nonn,more
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AUTHOR
| Daniel Tisdale (daniel6874(AT)gmail.com), May 25 2009
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EXTENSIONS
| a(6) - a(16) from Robert G. Wilson v (rgwv(AT)rgwv.com), Jun 05 2009
a(17) - a(19) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Sep 16 2009
Edited by N. J. A. Sloane, May 11 2010
a(20) from Donovan Johnson (donovan.johnson(AT)yahoo.com), May 20 2010
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