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 A322372 Least positive integer c such that c*prime(n) is practical. 1
 1, 2, 4, 4, 6, 6, 12, 12, 12, 12, 16, 18, 20, 20, 24, 24, 24, 24, 30, 30, 30, 36, 36, 36, 42, 48, 48, 48, 48, 48, 60, 60, 60, 60, 60, 60, 60, 60, 60, 72, 72, 72, 72, 72, 84, 84, 84, 84, 90, 90, 90, 96, 96, 96, 108, 108, 108, 108, 108, 108, 120, 120, 120, 120, 120 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE For n = 4 we have prime(n) = prime(4) = 7. The least k such that k*prime(4) is practical is k = 4, to get 28. Therefore, a(4) = 4. PROG (PARI) a(n) = my(p = prime(n)); for(i = 1, oo, if(is_A005153(p * i), return(i))) \\ David A. Corneth, Dec 31 2018 CROSSREFS Cf. A005153. Sequence in context: A135974 A153494 A205404 * A316945 A307370 A014246 Adjacent sequences:  A322369 A322370 A322371 * A322373 A322374 A322375 KEYWORD nonn AUTHOR David A. Corneth, Dec 05 2018 STATUS approved

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Last modified June 19 04:44 EDT 2019. Contains 324217 sequences. (Running on oeis4.)