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 A249242 #25 Jun 26 2019 05:40:48 %S A249242 30,42,66,70,78,102,114,138,174,186,222,246,258,282,318,354,366,402, %T A249242 426,438,474,498,534,582,606,618,642,654,678,762,786,822,834,894,906, %U A249242 942,978,1002,1038,1074,1086,1146,1158,1182,1194,1266,1338,1362,1374,1398,1430,1434,1446,1506 %N A249242 Squarefree primitive abundant numbers (using the second definition: having no abundant proper divisors, cf. A091191). %C A249242 Primitive numbers in A087248. %C A249242 Squarefree numbers in A091191. %C A249242 According to the definition of A091191, all terms of the form 6*p, p > 3, are in this sequence (and similarly for other perfect numbers). Primitive abundant can also be defined as "having only deficient proper divisors", cf. A071395. The corresponding squarefree terms are listed in A298973, and those with n prime factors are counted in A295369. (The preceding remark shows that this count would be infinite for n = 3, using the definition of A091191.) - _M. F. Hasler_, Feb 16 2018 %H A249242 Amiram Eldar, <a href="/A249242/b249242.txt">Table of n, a(n) for n = 1..10000</a> %t A249242 Select[Range@1506, SquareFreeQ[#] && DivisorSigma[1, #] > 2 # && Times @@ Boole@ Map[DivisorSigma[1, #] <= 2 # &, Most@ Divisors@ #] == 1 &] (* _Amiram Eldar_, Jun 26 2019 after _Michael De Vlieger_ at A091191 *) %o A249242 (PARI) v=[];for(n=1,10^5,d=0;for(j=2,ceil(sqrt(n)),if(n%(j^2),d++));if(d==ceil(sqrt(n))-1,if(sigma(n)>2*n,c=0;for(i=1,#v,if(n%v[i],c++));if(c==#v,print1(n,", ");v=concat(v,n))))) %Y A249242 Intersection of A087248 and A091191. %Y A249242 Cf. A071395, A295369, A298973. %K A249242 nonn %O A249242 1,1 %A A249242 _Derek Orr_, Oct 23 2014 %E A249242 Definition edited by _M. F. Hasler_, Feb 16 2018