A322372 Least positive integer c such that c*prime(n) is practical.

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

David A. Corneth, Table of n, a(n) for n = 1..10000

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, A267124.

Sequence in context: A153494 A352749 A205404 * A330812 A368200 A316945

Adjacent sequences: A322369 A322370 A322371 * A322373 A322374 A322375

Keyword

nonn

Author

David A. Corneth, Dec 05 2018

Status

approved