A290490 - OEIS

%I #19 Jul 23 2021 02:08:45

%S 1,2,6,10,14,18,22,26,30,42,60,66,78,102,114,138,150,174,186,210,330,

%T 390,462,510,546,570,690,798,858,870,930,1050,1110,1218,1230,1290,

%U 1410,1470,1590,1722,1770,1830,2010,2130,2190,2310,2730,3570,3990,4290,4830,5610,6006,6090,6510,7410,7590,7770

%N Numbers k such that (sum of proper unitary divisors of k) > (sum of proper unitary divisors of m) for all m < k.

%C Numbers k such that A034460(k) > A034460(m) for all m < k.

%H Amiram Eldar, <a href="/A290490/b290490.txt">Table of n, a(n) for n = 1..1000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/UnitaryDivisor.html">Unitary Divisor</a>

%H <a href="/index/Su#sums_of_divisors">Index entries for sequences related to sums of divisors</a>

%t mx = -1; t = {}; Do[u = DivisorSum[n, # &, GCD[#, n/#] == 1 &] - n; If[u > mx, mx = u; AppendTo[t, n]], {n, 8000}]; t

%o (PARI) sumud(n) = sumdiv(n, d, if (gcd(d, n/d)==1, d)) - n;

%o lista(nn) = {lasts = -1; for (n=1, nn, if ((news = sumud(n)) > lasts, print1(n, ", "); lasts = news););} \\ _Michel Marcus_, Aug 04 2017

%Y Cf. A002182, A002093, A034090, A034448, A034460, A063919, A280013, A281782, A285614.

%K nonn

%O 1,2

%A _Ilya Gutkovskiy_, Aug 03 2017