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Search: id:A072820
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| A072820 |
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Largest number of distinct primes to represent n as arithmetic mean. |
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+0
2
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| 1, 1, 3, 3, 5, 4, 5, 5, 7, 6, 9, 8, 9, 9, 11, 10, 11, 11, 13, 12, 13, 13, 15, 14, 17, 15, 17, 16, 17, 17, 19, 18, 19, 19, 21, 20, 23, 21, 23, 22, 23, 23, 25, 24, 25, 25, 27, 26, 27, 27, 29, 28, 29, 28, 29, 29, 31, 30, 31, 31, 33, 32, 33, 33, 35, 33, 35, 34, 37, 35, 37, 36, 37, 37
(list; graph; listen)
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OFFSET
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2,3
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LINKS
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Reinhard Zumkeller, Representing integers as arithmetic means of primes
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EXAMPLE
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a(20)=7: (2+3+5+23+29+31+47)/7 = 20.
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MAPLE
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Contribution from Alois P. Heinz (heinz(AT)hs-heilbronn.de), Aug 03 2009: (Start)
sp:= proc(i) option remember; `if` (i=1, 2, sp(i-1) +ithprime(i)) end:
b:= proc(n, i, t) local h; if n<0 then 0 elif n=0 then `if` (t=0, 1, 0) elif i=2 then `if` (n=2 and t=1, 1, 0) else h := b(n, prevprime(i), t); b(n, i, t):= `if` (h>0, h, b(n-i, prevprime(i), t-1)) fi end:
a:= proc(n) local i, k; if n<4 then 1 else for k from 2 while sp(k)/k<=n do od: do k:= k-1; if b(k*n, nextprime (k*n -sp(k-1)-1), k)>0 then break fi od; k fi end: seq (a(n), n=2..50); (End)
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CROSSREFS
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Cf. A072701.
Sequence in context: A094439 A122037 A008316 this_sequence A131950 A116192 A090104
Adjacent sequences: A072817 A072818 A072819 this_sequence A072821 A072822 A072823
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jul 15 2002
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EXTENSIONS
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More terms from Alois P. Heinz (heinz(AT)hs-heilbronn.de), Aug 03 2009
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