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A326158 Nonprime squarefree numbers whose product of prime indices is divisible by their sum of prime indices. 11

%I #8 Jan 11 2021 02:50:26

%S 30,65,154,165,190,259,273,385,390,435,442,481,506,561,595,609,658,

%T 714,741,781,874,935,1001,1110,1118,1173,1254,1281,1330,1363,1403,

%U 1430,1455,1469,1495,1505,1653,1691,1771,1786,1794,1798,1887,1958,2035,2067,2139

%N Nonprime squarefree numbers whose product of prime indices is divisible by their sum of prime indices.

%C 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.

%H Amiram Eldar, <a href="/A326158/b326158.txt">Table of n, a(n) for n = 1..10000</a>

%e The sequence of terms together with their prime indices begins:

%e 30: {1,2,3}

%e 65: {3,6}

%e 154: {1,4,5}

%e 165: {2,3,5}

%e 190: {1,3,8}

%e 259: {4,12}

%e 273: {2,4,6}

%e 385: {3,4,5}

%e 390: {1,2,3,6}

%e 435: {2,3,10}

%e 442: {1,6,7}

%e 481: {6,12}

%e 506: {1,5,9}

%e 561: {2,5,7}

%e 595: {3,4,7}

%e 609: {2,4,10}

%e 658: {1,4,15}

%e 714: {1,2,4,7}

%e 741: {2,6,8}

%e 781: {5,20}

%t primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];

%t Select[Range[2,1000],!PrimeQ[#]&&SquareFreeQ[#]&&Divisible[Times@@primeMS[#],Plus@@primeMS[#]]&]

%Y Satisfies A056239(a(n))|A003963(a(n)).

%Y The case with squarefree numbers included is A326150.

%Y The case with primes and squarefree numbers included is A326149.

%Y Cf. A057567, A057568, A112798, A301987.

%Y Cf. A325037, A325042, A325044, A326151, A326153/A326154, A326155, A326156.

%K nonn

%O 1,1

%A _Gus Wiseman_, Jun 10 2019

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Last modified April 24 19:24 EDT 2024. Contains 371962 sequences. (Running on oeis4.)