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 A281995 #18 Feb 16 2017 03:18:40 %S A281995 1,3,5,6,7,10,11,13,14,15,17,19,21,22,23,26,29,31,33,34,35,37,38,39, %T A281995 41,43,46,47,51,53,55,57,58,59,61,62,65,66,67,69,71,73,74,77,79,83,85, %U A281995 86,87,89,91,93,94,95,97,101,103,106,107,109,111,113,114,115,118 %N A281995 Squarefree numbers that, when added to the sum of their prime factors, remain squarefree. %H A281995 Robert Israel, <a href="/A281995/b281995.txt">Table of n, a(n) for n = 1..10000</a> %e A281995 a(6) = 10 = 2*5 that is squarefree. 10 + 2 + 5 = 17 = 1*17, which is also squarefree. %e A281995 a(14) = 22 = 2*11 that is squarefree. 22 + 2 + 11 = 35 = 5*7, which is also squarefree. %e A281995 a(219) = 434 = 2*7*31 that is squarefree. 434 + 2 + 7 + 31 = 474 = 2*3*79, which is also squarefree. %p A281995 filter:= n -> numtheory:-issqrfree(n) and numtheory:-issqrfree(n+convert(numtheory:-factorset(n),`+`)): %p A281995 select(filter, [$1..1000]); # _Robert Israel_, Feb 15 2017 %t A281995 Select[Range[500], SquareFreeQ[#] && SquareFreeQ[# + Total[Times @@@ FactorInteger[#]]] &] %o A281995 (PARI) isok(n) = issquarefree(n) && issquarefree(n + vecsum(factor(n)[, 1])); \\ _Michel Marcus_, Feb 05 2017 %Y A281995 Cf. A001414, A005117, A050703. %K A281995 nonn %O A281995 1,2 %A A281995 _K. D. Bajpai_, Feb 04 2017