A234517 - OEIS

%I #14 Dec 12 2014 16:20:42

%S 2,4,6,12,24,36,60,72,120,180,240,360,420,480,720,840,1260,1680,2520,

%T 5040,7560,10080,12600,15120,20160,27720,30240,32760,55440,65520,

%U 83160,110880,131040,166320,196560,221760,277200,332640,360360,393120,415800,443520

%N Sequence of numbers from A234515 such that A234515(n) > A234515(k) for all k < n.

%C A234515 = natural numbers n sorted by decreasing values of number k(n) = log_n(sigma(n)), where sigma(n) = A000203(n) = the sum of divisors of n.

%C Conjecture:  sequence a(n) for n >= 4 is not the same as sequence of numbers from A234516 such that A234516(n) > A234516(k) for all k < n.

%o (PARI) lista(nn) = {v = vector(nn, n, if (n==1, 0, log(sigma(n))/log(n))); v = vecsort(v,,5); m = 0; for (n=1, #v, if (v[n] > m, m = v[n]; print1(m, ", ")););} \\ _Michel Marcus_, Dec 11 2014

%Y Cf. A002182 (numbers n such that tau(n) > tau(k) for all k < n), A002473 (numbers whose prime divisors are all <= 7).

%Y Cf. A234515, A234516, A234518, A234519, A234520, A234521, A234522, A234523, A234524.

%K nonn

%O 1,1

%A _Jaroslav Krizek_, Jan 03 2014

%E 480 inserted and more terms from _Michel Marcus_, Dec 11 2014