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

1,1

Comments

The first of two consecutive numbers in A033942.

Links

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

Example

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.

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 &]

Prog

(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

Crossrefs

Cf. A033942, A344843.

Sequence in context: A114446 A141229 A253919 * A259504 A307373 A121614

Adjacent sequences: A357074 A357075 A357076 * A357078 A357079 A357080

Keyword

nonn

Author

Tanya Khovanova, Sep 10 2022

Status

approved