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 A100802 a(n) = least k >= 0 such that (n+k)/2 is prime. 2
 4, 3, 2, 1, 0, 1, 0, 3, 2, 1, 0, 3, 2, 1, 0, 7, 6, 5, 4, 3, 2, 1, 0, 3, 2, 1, 0, 7, 6, 5, 4, 3, 2, 1, 0, 3, 2, 1, 0, 7, 6, 5, 4, 3, 2, 1, 0, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 3, 2, 1, 0, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 7, 6, 5, 4, 3, 2, 1, 0, 3, 2, 1, 0, 7, 6, 5, 4, 3, 2, 1, 0, 11, 10, 9, 8, 7, 6, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS If a(n) = k is nonzero then a(n+1) = k-1. a(2p) = 0 for p prime. LINKS Harvey P. Dale, Table of n, a(n) for n = 0..1000 MATHEMATICA a = {}; Do[k = 0; While[ ! PrimeQ[(n + k)/2], k++ ]; AppendTo[a, k]; , {n, 0, 120}]; a (Chandler) lk[n_]:=Module[{k=If[EvenQ[n], 0, 1]}, While[!PrimeQ[(n+k)/2], k=k+2]; k]; Array[lk, 120, 0] (* Harvey P. Dale, Nov 25 2016 *) CROSSREFS Cf. A100803. Sequence in context: A067018 A200233 A239475 * A022960 A023446 A258447 Adjacent sequences:  A100799 A100800 A100801 * A100803 A100804 A100805 KEYWORD nonn,easy AUTHOR Amarnath Murthy, Dec 18 2004 EXTENSIONS Extended by Ray Chandler, Jan 19 2005 STATUS approved

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Last modified September 23 17:41 EDT 2017. Contains 292362 sequences.