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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.

A321453 Numbers that cannot be factored into two or more factors all having the same sum of prime indices.

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%I A321453 #6 Nov 13 2018 12:54:32
%S A321453 1,2,3,5,6,7,10,11,13,14,15,17,18,19,20,21,22,23,24,26,28,29,31,33,34,
%T A321453 35,37,38,39,41,42,43,44,45,46,47,50,51,52,53,54,55,56,57,58,59,60,61,
%U A321453 62,65,66,67,68,69,71,72,73,74,75,76,77,78,79,80,82,83,85
%N A321453 Numbers that cannot be factored into two or more factors all having the same sum of prime indices.
%C A321453 Also Heinz numbers of integer partitions that cannot be partitioned into two or more blocks with equal sums. The Heinz number of an integer partition (y_1, ..., y_k) is prime(y_1) * ... * prime(y_k).
%C A321453 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. The sum of prime indices of n is A056239(n).
%e A321453 The sequence of all integer partitions that cannot be partitioned into two or more blocks with equal sums begins: (1), (2), (3), (21), (4), (31), (5), (6), (41), (32), (7), (221), (8), (311), (42), (51), (9), (2111), (61), (411).
%t A321453 hwt[n_]:=Total[Cases[FactorInteger[n],{p_,k_}:>PrimePi[p]*k]];
%t A321453 facs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[facs[n/d],Min@@#>=d&]],{d,Rest[Divisors[n]]}]];
%t A321453 Select[Range[100],Select[facs[#],And[Length[#]>1,SameQ@@hwt/@#]&]=={}&]
%Y A321453 Positions of 1's in A321455.
%Y A321453 Cf. A056239, A112798, A276024, A279787, A305551, A306017, A317144, A320322, A321451, A321452, A321454.
%K A321453 nonn
%O A321453 1,2
%A A321453 _Gus Wiseman_, Nov 10 2018