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 A327685 #5 Sep 23 2019 13:43:40 %S A327685 9,21,25,27,39,49,57,63,65,81,87,91,111,115,117,121,125,129,133,147, %T A327685 159,169,171,183,185,189,203,213,235,237,243,247,259,261,267,273,289, %U A327685 299,301,303,305,319,321,325,333,339,343,351,361,365,371,377,387,393,399 %N A327685 Nonprime numbers whose prime indices have a common divisor > 1. %C A327685 First differs from A322336 in lacking 2535 = prime(2)*prime(3)*prime(6)^2. %C A327685 A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798. Heinz numbers of integer partitions with a common divisor > 1 are A318978, and the enumeration of these partitions by sum is A108572. %F A327685 Complement of A000040 in A318978. %e A327685 The sequence of terms together with their prime indices begins: %e A327685 9: {2,2} %e A327685 21: {2,4} %e A327685 25: {3,3} %e A327685 27: {2,2,2} %e A327685 39: {2,6} %e A327685 49: {4,4} %e A327685 57: {2,8} %e A327685 63: {2,2,4} %e A327685 65: {3,6} %e A327685 81: {2,2,2,2} %e A327685 87: {2,10} %e A327685 91: {4,6} %e A327685 111: {2,12} %e A327685 115: {3,9} %e A327685 117: {2,2,6} %e A327685 121: {5,5} %e A327685 125: {3,3,3} %e A327685 129: {2,14} %e A327685 133: {4,8} %e A327685 147: {2,4,4} %t A327685 Select[Range[100],#>1&&!PrimeQ[#]&&GCD@@PrimePi/@First/@FactorInteger[#]>1&] %Y A327685 Cf. A000837, A007916, A018783, A056239, A108572, A112798, A289509, A318978, A327407, A327658. %K A327685 nonn %O A327685 1,1 %A A327685 _Gus Wiseman_, Sep 22 2019