login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A006073 Numbers n such that n, n+1 and n+2 all have same number of distinct prime divisors. 14
2, 3, 7, 20, 33, 34, 38, 44, 50, 54, 55, 56, 74, 75, 85, 86, 91, 92, 93, 94, 98, 115, 116, 117, 122, 133, 134, 141, 142, 143, 144, 145, 146, 158, 159, 160, 175, 176, 183, 187, 200, 201, 205, 206, 207, 212, 213, 214, 215, 216, 217, 224, 235, 247 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Distinct prime divisors means that the prime divisors are counted without multiplicity. - Harvey P. Dale, Apr 19 2011

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..10000

MATHEMATICA

pdQ[n_]:=PrimeNu[n]==PrimeNu[n+1]==PrimeNu[n+2]; Select[Range[250], pdQ] (* Harvey P. Dale, Apr 19 2011 *)

Take[Transpose[Flatten[Select[Partition[{#, PrimeNu[#]}&/@Range[250000], 3, 1], #[[1, 2]]==#[[2, 2]]==#[[3, 2]]&], 1]][[1]], {1, -1, 3}] (* Harvey P. Dale, Dec 09 2011 *)

Flatten[Position[Partition[PrimeNu[Range[250]], 3, 1], _?(#[[1]]==#[[2]]== #[[3]]&), {1}, Heads->False]] (* Harvey P. Dale, Oct 30 2013 *)

CROSSREFS

Cf. A006049, A045932.

Sequence in context: A172976 A171655 A293683 * A052402 A300041 A222939

Adjacent sequences:  A006070 A006071 A006072 * A006074 A006075 A006076

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 11 00:32 EDT 2020. Contains 336403 sequences. (Running on oeis4.)