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 A280946 #12 Jan 14 2017 07:46:40
%S A280946 1,8,9,10,12,14,18,22,24,25,26,28,30,32,34,35,38,40,44,46,49,52,54,55,
%T A280946 58,60,62,63,65,66,68,72,74,76,77,78,80,81,82,84,85,86,88,90,91,92,94,
%U A280946 95,96,98,99,102,104,106,108,110,112,114,115,116,117,118,119,121,122,124,125,126,128,130,133,134,135,136,138
%N A280946 Numbers n such that n and number of proper divisors (A032741) of n are relatively prime and n is a nonprime (A018252).
%C A280946 Numbers n such that A125168(n) = 1 and A010051(n) = 0.
%C A280946 Numbers n such that gcd(n,A032741(n)) = 1 and A000005(n) != 2.
%H A280946 Vincenzo Librandi, <a href="/A280946/b280946.txt">Table of n, a(n) for n = 1..3000</a>
%e A280946 12 is in the sequence because 12 is a nonprime, 12 has 5 proper divisors {1, 2, 3, 4, 6} and gcd(12,5) = 1.
%t A280946 Select[Range[139], CoprimeQ[#1, DivisorSigma[0, #1] - 1] && !PrimeQ[#1] & ]
%t A280946 Select[Range[139], GCD[#1, DivisorSigma[0, #1] - 1] == 1 && DivisorSigma[0, #1] != 2 &]
%o A280946 (PARI) isok(n) = gcd(n, numdiv(n)-1) == 1; \\ _Michel Marcus_, Jan 14 2017
%Y A280946 Cf. A000005, A003624, A010051, A014567, A032741, A046642, A125168.
%K A280946 nonn,easy
%O A280946 1,2
%A A280946 _Ilya Gutkovskiy_, Jan 11 2017