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A327900 Nonprime squarefree numbers whose prime indices all have the same Omega (number of prime factors counted with multiplicity). 3
1, 15, 33, 51, 55, 85, 91, 93, 123, 155, 161, 165, 177, 187, 201, 203, 205, 249, 255, 295, 299, 301, 327, 329, 335, 341, 377, 381, 415, 451, 465, 471, 511, 527, 537, 545, 553, 559, 561, 573, 611, 615, 633, 635, 649, 667, 679, 697, 703, 707, 723, 737, 785, 831 (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: {}
15: {2,3}
33: {2,5}
51: {2,7}
55: {3,5}
85: {3,7}
91: {4,6}
93: {2,11}
123: {2,13}
155: {3,11}
161: {4,9}
165: {2,3,5}
177: {2,17}
187: {5,7}
201: {2,19}
203: {4,10}
205: {3,13}
249: {2,23}
255: {2,3,7}
295: {3,17}
MATHEMATICA
Select[Range[1000], !PrimeQ[#]&&SquareFreeQ[#]&&SameQ@@PrimeOmega/@PrimePi/@First/@FactorInteger[#]&]
CROSSREFS
The case including primes and nonsquarefree numbers is A320324.
The version for sum of prime indices is A327901.
The version for mean of prime indices is A327902.
Sequence in context: A316153 A190754 A357934 * A071965 A242677 A020184
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 30 2019
STATUS
approved

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Last modified March 29 08:13 EDT 2024. Contains 371265 sequences. (Running on oeis4.)