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 A071572 Least k such that nextprime(k*prime(n)) - k*prime(n) is nonprime. 1
 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, 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, 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS 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. LINKS MATHEMATICA 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}] CROSSREFS Sequence in context: A144387 A030768 A051480 * A172176 A285930 A300480 Adjacent sequences:  A071569 A071570 A071571 * A071573 A071574 A071575 KEYWORD nonn AUTHOR David W. Wilson and Robert G. Wilson v, May 31 2002 STATUS approved

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Last modified November 26 21:07 EST 2021. Contains 349344 sequences. (Running on oeis4.)