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 A224988 #16 Oct 29 2019 09:03:18 %S A224988 2217231104,6221622528,9644780288,12127073024,15377570560,15520617728, %T A224988 22426778880,25138541824,34766068480,43551357696,49424655104, %U A224988 56022543104,67513462016,84107119360,84889511168,90906475264,107642993920,156987452160,174347951360,175969792768 %N A224988 Even RMS numbers: even numbers n such that root mean square of divisors of n is an integer. %C A224988 Even numbers from A140480. %C A224988 The first 20 terms are all divisible by 30976. 30976 = 2^8*11^2. %C A224988 a(21) > 2*10^11. %C A224988 All the 83 terms up to 10^13 are divisible by 30976. - _Giovanni Resta_, Oct 29 2019 %H A224988 Giovanni Resta, <a href="/A224988/b224988.txt">Table of n, a(n) for n = 1..83</a> (terms < 10^13) %H A224988 Donovan Johnson, <a href="/A224988/a224988_1.txt">177 terms > 2*10^11</a> %F A224988 Even numbers n such that A001157(n)/A000005(n) is a square. %e A224988 n = 2217231104 (even). sigma_2(n) = 6616291782395055852. n has 108 divisors. 6616291782395055852/108 = 247511537^2. %o A224988 (PARI) forstep(n=2, 10^10, 2, s=sigma(n, 2); nd=numdiv(n); if(s%nd==0, if(issquare(s\nd), print(n)))) %o A224988 (PARI) isok(n) = my(s=sigma(n, 2), nd=numdiv(n)); if(s%nd==0, issquare(s\nd), 0); \\ program adapted by _Michel Marcus_, Oct 29 2019 %Y A224988 Cf. A000005, A001157, A140480. %K A224988 nonn %O A224988 1,1 %A A224988 _Donovan Johnson_, Apr 25 2013