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A067316 a(n) is the number of values of j, 0 <= j <= n, such that 1 + binomial(n,j) is prime. 1

%I

%S 1,2,3,2,5,4,4,2,5,6,6,6,6,4,5,2,6,8,8,6,6,4,4,2,11,4,4,8,8,8,4,2,6,4,

%T 8,14,8,4,5,6,12,10,4,6,9,8,8,4,6,8,6,10,6,6,12,6,8,4,12,2,6,8,4,2,8,

%U 18,8,2,6,14,10,16,10,6,4,10,13,8,12,4,8,2,8,14,2,6,4,10,10,16,10,10,9

%N a(n) is the number of values of j, 0 <= j <= n, such that 1 + binomial(n,j) is prime.

%e For n=8, the primes are 2,29,71,29,2, so a(n)=5.

%e a(n)=6 for n=9,10,11,12. Also, a(n)=10 for n=149,...,154.

%t a[n_] := Count[Table[PrimeQ[Binomial[n, w]+1], {w, 0, n}], True]

%o (PARI) a(n) = sum(j=0, n, isprime(1 + binomial(n,j))); \\ _Michel Marcus_, Oct 30 2018

%K nonn

%O 0,2

%A _Labos Elemer_, Jan 15 2002

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Last modified September 24 21:51 EDT 2022. Contains 356949 sequences. (Running on oeis4.)