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Search: id:A103622
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| A103622 |
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Smallest arithmetic mean of n distinct primes. |
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+0
1
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| 2, 4, 4, 7, 6, 11, 10, 13, 12, 17, 16, 21, 20, 24, 24, 29, 26, 32, 32, 36, 36, 41, 38, 45, 44, 49, 48, 53, 52, 58, 58, 63, 62, 68, 66, 72, 70, 77, 76, 83, 80, 87, 86, 92, 90, 97, 96, 102, 100, 108, 106, 113, 110, 118, 116, 123, 122, 129, 126, 133, 132, 139, 138, 145, 142
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Often a(2n+1)=a(2n)-1. - Robert G. Wilson v Jan 19 2007
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EXAMPLE
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a(1)=2 because (2)/1=2,
a(2)=4 because (3+5)/2=4,
a(3)=4 because (2+3+7)/3=4,
a(4)=7 because (3+5+7+13)/4=7,
a(5)=6 because (2+3+5+7+13)/5=6,
a(6)=11 because (3+5+7+11+17+23)/6=11,
a(7)=10 because (2+3+5+7+11+13+29)/7=10,
a(8)=13 because (3+5+7+11+13+17+19+29)/8=13,
a(9)=12 because (2+3+5+7+11+13+17+19+31)/9=12,
a(10)=17 because (3+5+7+11+13+17+19+23+29+43)/10=17, etc.
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MATHEMATICA
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f[n_] := Block[{k = 1, lst = Prime@ Range[ If[ OddQ@ n, 1, 2], n + 3]}, While[ Mod[Plus @@ Flatten@Subsets[lst, {n}, {k}], n] != 0, k++ ]; (Plus @@ Flatten@ Subsets[lst, {n}, {k}])/n]; Array[f, 65] (* Robert G. Wilson v *)
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CROSSREFS
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Cf. A072701.
Sequence in context: A104510 A082515 A062855 this_sequence A105774 A130805 A023831
Adjacent sequences: A103619 A103620 A103621 this_sequence A103623 A103624 A103625
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KEYWORD
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easy,nonn
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AUTHOR
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Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Mar 25 2005
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EXTENSIONS
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Edited, corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 19 2007
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