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Search: id:A059998
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| A059998 |
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Number of different primes occurring when n is expressed as p1+q1+r1 = ... = pk+qk+rk where pk,qk,rk are primes with pk <= qk <= rk. |
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3
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| 0, 0, 0, 0, 0, 1, 2, 2, 3, 3, 4, 4, 3, 3, 5, 4, 6, 5, 5, 5, 7, 5, 8, 6, 7, 7, 9, 6, 8, 5, 8, 7, 10, 5, 11, 8, 10, 9, 10, 4, 12, 7, 11, 9, 13, 7, 14, 8, 13, 11, 15, 9, 14, 7, 14, 11, 16, 7, 15, 8, 15, 13, 17, 6, 18, 11, 17, 13, 17, 5, 19, 11, 18, 13, 20, 10, 21, 11, 20, 15, 20, 9, 22, 10, 21
(list; graph; listen)
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OFFSET
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1,7
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COMMENT
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Goldbach conjectured that every integer >5 is the sum of three primes. 6=2+2+2, 7=2+2+3, 8=2+3+3, 9=3+3+3=2+2+5,......
The largest possible value of a(n) is PrimePi(n)-1, which is frequently attained. - T. D. Noe, May 05 2008
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..2000
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FORMULA
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If n is of the form 2*(prime + 1) then a(n) is an even number.
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EXAMPLE
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n=9: 9 = 3+3+3 = 2+2+5, we can see 3 different primes. so a(9) = 3.
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CROSSREFS
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Sequence in context: A084054 A106747 A083447 this_sequence A036041 A085654 A074719
Adjacent sequences: A059995 A059996 A059997 this_sequence A059999 A060000 A060001
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KEYWORD
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easy,nonn,nice
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AUTHOR
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Naohiro Nomoto (6284968128(AT)geocities.co.jp), Mar 10 2001
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