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 A084821 #11 Sep 12 2019 14:59:14 %S A084821 15,45,63,75,105,135,165,189,195,225,231,255,273,285,297,315,345,357, %T A084821 375,399,405,429,435,441,465,483,495,525,555,567,585,609,615,645,651, %U A084821 675,693,705,735,765,777,795,819,825,855,861,885,891,903,915,945,975 %N A084821 Odd numbers m such that sigma(m) > m + phi(m), where sigma=A000203 is the divisor sum and phi=A000010 the totient. %C A084821 This sequence is closed under multiplication by odd values, and in particular with multiplication by itself. - _Charles R Greathouse IV_, Feb 19 2013 %H A084821 Amiram Eldar, <a href="/A084821/b084821.txt">Table of n, a(n) for n = 1..10000</a> %t A084821 Select[Range[1, 1000, 2], DivisorSigma[1, #] > EulerPhi[#] + # &] (* _Amiram Eldar_, Sep 12 2019 *) %o A084821 (PARI) is(n)=n%2 && sigma(n)>eulerphi(n)+n \\ _Charles R Greathouse IV_, Feb 19 2013 %Y A084821 Cf. A000010, A000203, A084820. %K A084821 nonn %O A084821 1,1 %A A084821 _Reinhard Zumkeller_, Jun 04 2003