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 A106790 Smallest k>0 such that binomial(n,k) + 1 is prime. 0
 1, 1, 3, 1, 2, 1, 7, 2, 2, 1, 4, 1, 2, 5, 15, 1, 2, 1, 4, 2, 2, 1, 23, 2, 6, 4, 4, 1, 7, 1, 31, 10, 6, 10, 4, 1, 18, 15, 9, 1, 2, 1, 17, 2, 2, 1, 23, 2, 4, 20, 6, 1, 6, 8, 10, 6, 2, 1, 59, 1, 2, 25, 63, 2, 2, 1, 67, 8, 2, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS a(n) <= n; for primes p: a(p-1) = 1. The values of n for which a(n)=n yield the sequence A067317. - Emeric Deutsch, Aug 27 2007 LINKS MAPLE a:=proc(n) local k: for k while isprime(1+binomial(n, k))=false do end do: k end proc: seq(a(n), n=1..70); # Emeric Deutsch, Aug 27 2007 MATHEMATICA a[n_] := For[k = 1, True, k++, If[PrimeQ[Binomial[n, k] + 1], Return[k]]]; Array[a, 70] (* Jean-François Alcover, Feb 13 2018 *) CROSSREFS Cf. A000040, A067317. Sequence in context: A008296 A140185 A229341 * A078897 A322034 A226629 Adjacent sequences:  A106787 A106788 A106789 * A106791 A106792 A106793 KEYWORD nonn AUTHOR Reinhard Zumkeller, May 16 2005 EXTENSIONS Corrected and extended by Emeric Deutsch, Aug 27 2007 STATUS approved

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Last modified October 19 15:50 EDT 2019. Contains 328223 sequences. (Running on oeis4.)