This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A322372 #17 Oct 16 2024 21:34:14 %S A322372 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, %T A322372 48,48,48,48,48,60,60,60,60,60,60,60,60,60,72,72,72,72,72,84,84,84,84, %U A322372 90,90,90,96,96,96,108,108,108,108,108,108,120,120,120,120,120 %N A322372 Least positive integer c such that c*prime(n) is practical. %C A322372 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 %H A322372 David A. Corneth, <a href="/A322372/b322372.txt">Table of n, a(n) for n = 1..10000</a> %e A322372 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. %o A322372 (PARI) a(n) = my(p = prime(n)); for(i = 1, oo, if(is_A005153(p * i), return(i))) \\ _David A. Corneth_, Dec 31 2018 %Y A322372 Cf. A005153, A267124. %K A322372 nonn %O A322372 1,2 %A A322372 _David A. Corneth_, Dec 05 2018