A357077 The lesser of two consecutive numbers with at least 3 prime factors (counted with multiplicity).

27, 44, 63, 75, 80, 98, 99, 104, 116, 124, 125, 135, 147, 152, 153, 164, 170, 171, 174, 175, 188, 189, 195, 207, 224, 230, 231, 242, 243, 244, 245, 255, 260, 272, 275, 279, 284, 285, 296, 315, 324, 332, 342, 343, 344, 350, 351, 356, 363, 368, 369, 374, 375, 384, 387, 399

Offset: 1

Author

Tanya Khovanova, Sep 10 2022

Keywords

• nonn

Comments

The first of two consecutive numbers in A033942.

Examples

			27 = 3^3 and 28 = 2^2 * 7. Thus, 27 and 28 both have at least three prime factors. Thus, 27 is in this sequence.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A033942, A344843.

Programs

Maple

R:= NULL: count:= 0: state:= 0:
for n from 1 while count < 100 do
  if numtheory:-bigomega(n) >= 3 then
     if state = 1 then R:= R, n-1; count:= count+1
     else state:= 1
     fi
  else state := 0
  fi
od:
R; # Robert Israel, Sep 16 2022

Mathematica

Select[Range[1000], Total[Transpose[FactorInteger[#]][[2]]] >= 3 && Total[Transpose[FactorInteger[# + 1]][[2]]] >= 3 &]

Python

from sympy import factorint
def is033942(n): return sum(factorint(n).values()) > 2
def ok(n): return is033942(n) and is033942(n+1)
print([k for k in range(400) if ok(k)]) # Michael S. Branicky, Sep 10 2022