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 A071572 Least k such that nextprime(k*prime(n)) - k*prime(n) is nonprime. 1

%I

%S 1,2,2,1,2,1,5,1,1,2,1,1,2,1,1,1,2,1,1,3,1,1,1,1,1,2,1,2,1,1,1,1,3,1,

%T 2,1,1,1,1,1,2,1,2,1,4,1,1,1,5,1,1,2,1,1,1,1,5,1,1,2,1,1,1,2,1,1,1,1,

%U 3,1,1,1,1,1,1,1,1,1,1,1,2,1,2,1,1,1,1,1,3,1,1,1,1,1,1,1,1,3,1,1,1,1,1,5,1

%N Least k such that nextprime(k*prime(n)) - k*prime(n) is nonprime.

%C The first time a value of m appears is when n equals 1, 2, 20, 45, 7. I can find no value greater than 5 for n's up through 12,500,000.

%t NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; f[n_] := Block[{k = 1}, While[ PrimeQ[ NextPrim[k*Prime[n]] - k*Prime[n]], k++ ]; k]; Table[ f[n], {n, 1, 105}]

%K nonn

%O 1,2

%A _David W. Wilson_ and _Robert G. Wilson v_, May 31 2002

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Last modified August 4 20:00 EDT 2020. Contains 336202 sequences. (Running on oeis4.)