A262359 - OEIS

%I #30 Oct 16 2023 01:18:01

%S 18,22932,14520576,1610563584,1907020800,2836487808,6399679104,

%T 70912195200,82819376640,159991977600,2732372020224,6164773235712,

%U 68309300505600,148068998977536,154119330892800,264727305267840,649657533767040,3701724974438400,42503412523106304,220312341220608000

%N Numbers k such that denominator(sigma(k)/k) = 6.

%H David A. Corneth, <a href="/A262359/b262359.txt">Table of n, a(n) for n = 1..54</a> (terms <= 10^28)

%e sigma(18)/18 = 13/6, hence 18 is a term.

%o (PARI) isok(n) = denominator(sigma(n, -1)) == 6;

%o (PARI) lista(nn) = {k = 6; nb = 0; while (nb != nn, if (denominator(sigma(k,-1)) == 6, print1(k, ", "); nb++); k += 6;);}

%Y Cf. similar sequences with A017666(n)=k: A159907 (k=2), A245775 (k=3), A229088 (k=4), A067237 (k=5).

%Y Cf. A000203.

%K nonn

%O 1,1

%A _Michel Marcus_, Sep 19 2015

%E a(10)-a(12) from _Jud McCranie_, Oct 14 2023

%E More terms from _David A. Corneth_, Oct 15 2023