A324522 Numbers > 1 where the minimum prime index is equal to the number of prime factors counted with multiplicity.

2, 9, 15, 21, 33, 39, 51, 57, 69, 87, 93, 111, 123, 125, 129, 141, 159, 175, 177, 183, 201, 213, 219, 237, 245, 249, 267, 275, 291, 303, 309, 321, 325, 327, 339, 381, 385, 393, 411, 417, 425, 447, 453, 455, 471, 475, 489, 501, 519, 537, 543, 573, 575, 579, 591

Offset

1,1

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.

Also Heinz numbers of integer partitions where the minimum part is equal to the number of parts (A006141). The Heinz number of an integer partition (y_1, ..., y_k) is prime(y_1) * ... * prime(y_k).

Links

Alois P. Heinz, Table of n, a(n) for n = 1..10000

Formula

A055396(a(n)) = A001222(a(n)).

Example

The sequence of terms together with their prime indices begins:
    2: {1}
    9: {2,2}
   15: {2,3}
   21: {2,4}
   33: {2,5}
   39: {2,6}
   51: {2,7}
   57: {2,8}
   69: {2,9}
   87: {2,10}
   93: {2,11}
  111: {2,12}
  123: {2,13}
  125: {3,3,3}
  129: {2,14}
  141: {2,15}
  159: {2,16}
  175: {3,3,4}

Maple

with(numtheory):
q:= n-> is(pi(min(factorset(n)))=bigomega(n)):
select(q, [$2..600])[];  # Alois P. Heinz, Mar 07 2019

Mathematica

Select[Range[2, 100], PrimePi[FactorInteger[#][[1, 1]]]==PrimeOmega[#]&]

Crossrefs

Cf. A001222, A006141, A055396, A056239, A106529, A112798, A256617.

Cf. A324515, A324517, A324519, A324521, A324522, A324560, A324562.

Sequence in context: A184531 A063105 A215035 * A319967 A063094 A369154

Adjacent sequences: A324519 A324520 A324521 * A324523 A324524 A324525

Keyword

nonn

Author

Gus Wiseman, Mar 06 2019

Status

approved