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Search: id:A085090
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| A085090 |
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Starting with n+(n-1) go on adding n-2, then n-3, etc. until one gets a prime; a(n) = smallest prime in n+(n-1)+(n-2)+...+(n-i) (with the least i that gives a prime), or 0 if no such prime exists. |
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+0
4
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| 0, 3, 5, 7, 0, 11, 13, 0, 17, 19, 0, 23, 0, 0, 29, 31, 0, 0, 37, 0, 41, 43, 0, 47, 0, 0, 53, 0, 0, 59, 61, 0, 0, 67, 0, 71, 73, 0, 0, 79, 0, 83, 0, 0, 89, 0, 0, 0, 97, 0, 101, 103, 0, 107, 109, 0, 113, 0, 0, 0, 0, 0, 0, 127, 0, 131, 0, 0, 137, 139, 0, 0, 0, 0, 149, 151, 0, 0, 157, 0, 0, 163
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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If 2n-1 is prime then a(n) = 2n-1, otherwise a(n) = 0. - David Wasserman (wasserma(AT)spawar.navy.mil), Jan 25 2005
a(A098090(n)-1)=2*A098090(n)-3; a(n)=(2*n-1)*A101264(n-1). - Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), Sep 14 2006
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EXAMPLE
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a(8) = 0 as there is no prime in the partial sum of the finite sequence 8,7,6,5,4,3,2,1.
a(7) = 13 = 7 + 6.
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CROSSREFS
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Cf. A122845.
Sequence in context: A099414 A099744 A024601 this_sequence A084713 A084712 A031100
Adjacent sequences: A085087 A085088 A085089 this_sequence A085091 A085092 A085093
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KEYWORD
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easy,nonn
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AUTHOR
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Amarnath Murthy and Meenakshi Srikanth (amarnath_murthy(AT)yahoo.com), Jul 02 2003
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EXTENSIONS
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More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Jan 25 2005
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