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A322372
Least positive integer c such that c*prime(n) is practical.
3
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
OFFSET
1,2
COMMENTS
All terms in this sequence are also practical numbers. All multiples c*prime(n) are also primitive practical numbers (A267124). - Frank M Jackson, Oct 16 2024
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
Sequence in context: A153494 A352749 A205404 * A330812 A368200 A316945
KEYWORD
nonn
AUTHOR
David A. Corneth, Dec 05 2018
STATUS
approved