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A063649 Largest b such that 1/n=1/c+1/b has integer solutions with c>b. +0
4
3, 4, 6, 6, 10, 8, 12, 12, 15, 12, 21, 14, 21, 24, 24, 18, 30, 20, 36, 30, 33, 24, 42, 30, 39, 36, 44, 30, 55, 32, 48, 44, 51, 60, 63, 38, 57, 52, 72, 42, 78, 44, 66, 72, 69, 48, 84, 56, 75, 68, 78, 54, 90, 80, 105, 76, 87, 60, 110, 62, 93, 112, 96, 90, 110, 68, 102, 92, 120 (list; graph; listen)
OFFSET

2,1

COMMENT

Smallest b is (n+1) since 1/n=1/(n(n+1))+1/(n+1)

FORMULA

a(n) =n*A063648(n)/(A063648(n)-n) =2n-A063428(n).

EXAMPLE

a(10)=15 since 1/10=1/20+1/20=1/30+1/15=1/35+1/14=1/60+1/12=1/110+1/11, but the first sum does not have c>b, leaving the second sum to provide the value.

CROSSREFS

Cf. A018892, A063427, A063428, A063647, A063648.

Sequence in context: A033095 A158907 A023830 this_sequence A053158 A158523 A001615

Adjacent sequences: A063646 A063647 A063648 this_sequence A063650 A063651 A063652

KEYWORD

nonn

AUTHOR

Henry Bottomley (se16(AT)btinternet.com), Jul 23 2001

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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