cp's OEIS Frontend

A324570 Numbers where the sum of distinct prime indices (A066328) is equal to the number of prime factors counted with multiplicity (A001222).

%I A324570 #11 Apr 13 2019 09:02:31
%S A324570 1,2,9,12,18,40,100,112,125,240,250,352,360,392,405,540,600,672,675,
%T A324570 810,832,900,1008,1125,1350,1372,1500,1512,1701,1875,1936,2112,2176,
%U A324570 2240,2250,2268,2352,2401,3168,3402,3528,3750,3969,4752,4802,4864,4992,5292
%N A324570 Numbers where the sum of distinct prime indices (A066328) is equal to the number of prime factors counted with multiplicity (A001222).
%C A324570 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. For example, 540 = prime(1)^2 * prime(2)^3 * prime(3)^1 has sum of distinct prime indices 1 + 2 + 3 = 6, while the number of prime factors counted with multiplicity is 2 + 3 + 1 = 6, so 540 belongs to the sequence.
%C A324570 Also Heinz numbers of the integer partitions counted by A114638. The Heinz number of an integer partition (y_1, ..., y_k) is prime(y_1) * ... * prime(y_k).
%F A324570 A066328(a(n)) = A001222(a(n)).
%e A324570 The sequence of terms together with their prime indices begins:
%e A324570     1: {}
%e A324570     2: {1}
%e A324570     9: {2,2}
%e A324570    12: {1,1,2}
%e A324570    18: {1,2,2}
%e A324570    40: {1,1,1,3}
%e A324570   100: {1,1,3,3}
%e A324570   112: {1,1,1,1,4}
%e A324570   125: {3,3,3}
%e A324570   240: {1,1,1,1,2,3}
%e A324570   250: {1,3,3,3}
%e A324570   352: {1,1,1,1,1,5}
%e A324570   360: {1,1,1,2,2,3}
%e A324570   392: {1,1,1,4,4}
%e A324570   405: {2,2,2,2,3}
%e A324570   540: {1,1,2,2,2,3}
%e A324570   600: {1,1,1,2,3,3}
%e A324570   672: {1,1,1,1,1,2,4}
%p A324570 with(numtheory):
%p A324570 q:= n-> is(add(pi(p), p=factorset(n))=bigomega(n)):
%p A324570 select(q, [$1..5600])[];  # _Alois P. Heinz_, Mar 07 2019
%t A324570 Select[Range[1000],Total[PrimePi/@First/@FactorInteger[#]]==PrimeOmega[#]&]
%Y A324570 Cf. A001221, A001222, A056239, A066328, A112798, A114638, A117144, A276078.
%Y A324570 Cf. A109298, A324524, A324525, A324570, A324571, A324572.
%K A324570 nonn
%O A324570 1,2
%A A324570 _Gus Wiseman_, Mar 07 2019