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Search: id:A092951
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| A092951 |
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Beginning with n add the next number, subtract the previous number and so on then a(n) = the largest prime arising in this process, or 0 if no prime is reached in 2n-1 steps: a(n) is the largest occurring prime in the sum n + (n+1) - (n-1) +(n+2) -(n-2) +(n+3)-(n-3)...+... + or - 1 occurring at any stage. |
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+0
2
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| 3, 5, 7, 17, 19, 37, 37, 41, 67, 101, 103, 73, 107, 197, 199, 257, 257, 157, 263, 401, 401, 269, 487, 577, 577, 677, 677, 281, 787, 421, 787, 593, 907, 797, 1091, 1297, 1297, 1301, 1447, 1601, 1601, 1453, 1607, 1609, 1459
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Conjecture: No term is zero.
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EXAMPLE
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a(5) = 19 and the steps are 5, 5+6, 5+6-4, 5+6-4+7, 5+6-4+7-3, 5+6-4+7-3+8, 5+6-4+7-3+8-2+9,5+6-4+7-3+8-2+9-1 and the numbers arising are 5,11,7,14,11,19,17,26,25. 19 is the largest prime.
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PROGRAM
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(GAP) A := function ( n ) local m, p, l, u; p := 0; u := n + 1; l := n - 1; m := n; if IsPrime( m ) then p := m; fi; repeat m := m + u; if IsPrime( m ) then p := m; fi; u := u + 1; m := m - l; if m > p and IsPrime( m ) then p := m; fi; l := l - 1; until l = 0; return p; end; (from Simon Nickerson (simonn(AT)maths.bham.ac.uk, Jun 29 2005)
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CROSSREFS
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Cf. A092950.
Sequence in context: A122395 A045401 A085499 this_sequence A001259 A087126 A062547
Adjacent sequences: A092948 A092949 A092950 this_sequence A092952 A092953 A092954
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Mar 24 2004
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EXTENSIONS
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More terms from Simon Nickerson (simonn(AT)maths.bham.ac.uk, Jun 29 2005)
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