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A327902 Nonprime squarefree numbers whose prime indices all have the same average of prime indices (A326567/A326568). 3
1, 21, 57, 115, 133, 145, 159, 371, 393, 399, 515, 535, 565, 667, 803, 869, 917, 933, 1007, 1067, 1113, 1963, 2021, 2095, 2157, 2165, 2177, 2249, 2285, 2315, 2363, 2369, 2461, 2489, 2599, 2705, 2751, 2839, 2987, 3021, 3103, 3277, 3335, 3707, 3859, 4331, 4367 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
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.
LINKS
EXAMPLE
The sequence of terms together with their prime indices begins:
1: {}
21: {2,4}
57: {2,8}
115: {3,9}
133: {4,8}
145: {3,10}
159: {2,16}
371: {4,16}
393: {2,32}
399: {2,4,8}
515: {3,27}
535: {3,28}
565: {3,30}
667: {9,10}
803: {5,21}
869: {5,22}
917: {4,32}
933: {2,64}
1007: {8,16}
1067: {5,25}
MATHEMATICA
primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Select[Range[1000], !PrimeQ[#]&&SquareFreeQ[#]&&SameQ@@Mean/@primeMS/@primeMS[#]&];
CROSSREFS
The version including primes and nonsquarefree numbers is A326536.
The version for number of prime indices is A327900.
The version for sum of prime indices is A327901.
Sequence in context: A044123 A044504 A118057 * A020148 A037305 A370109
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 30 2019
STATUS
approved

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Last modified March 28 12:26 EDT 2024. Contains 371254 sequences. (Running on oeis4.)