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 A321516 #17 Jun 20 2023 10:04:13 %S A321516 0,0,0,0,0,0,0,1,0,0,0,2,0,0,0,2,0,2,0,2,0,0,0,4,0,0,1,2,0,3,0,3,0,0, %T A321516 0,5,0,0,0,4,0,3,0,2,2,0,0,6,0,2,0,2,0,4,0,4,0,0,0,7,0,0,2,4,0,3,0,2, %U A321516 0,3,0,8,0,0,2,2,0,3,0,6,2,0,0,7,0,0,0 %N A321516 Number of composite divisors of n that are < n. %C A321516 Different from A294902 (see A321517). %C A321516 a(n) > 0 iff n is a term of A033942. %H A321516 Michael De Vlieger, <a href="/A321516/b321516.txt">Table of n, a(n) for n = 1..10000</a> %e A321516 For n = 24: The divisors of 24 are 1, 2, 3, 4, 6, 8, 12, 24. Four of those divisors, namely 4, 6, 8 and 12 are composite and < 24, so a(24) = 4. %t A321516 a[n_] := Length[Select[Most[Divisors[n]], CompositeQ]]; Array[a, 87] (* _Amiram Eldar_, Nov 12 2018 *) %o A321516 (PARI) a(n) = my(d=divisors(n), i=0); for(k=2, #d-1, if(!ispseudoprime(d[k]), i++)); i %o A321516 (PARI) a(n) = sumdiv(n, d, (d<n) && (d>1) && !isprime(d)); \\ _Michel Marcus_, Nov 12 2018 %Y A321516 Cf. A033942, A294902, A321517. %K A321516 nonn %O A321516 1,12 %A A321516 _Felix Fröhlich_, Nov 12 2018