login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A102467 Numbers such that the sum of numbers of prime factors with and without repetitions does not equal the number of divisors. 8
1, 12, 18, 20, 24, 28, 30, 36, 40, 42, 44, 45, 48, 50, 52, 54, 56, 60, 63, 66, 68, 70, 72, 75, 76, 78, 80, 84, 88, 90, 92, 96, 98, 99, 100, 102, 104, 105, 108, 110, 112, 114, 116, 117, 120, 124, 126, 130, 132, 135, 136, 138, 140, 144, 147, 148, 150, 152, 153, 154, 156 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Complement of A102466; A000005(a(n)) <> A001221(a(n)) + A001222(a(n)).

For n > 1: A086971(a(n)) > 1. - Reinhard Zumkeller, Dec 14 2012

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

FORMULA

These are the numbers which are neither prime powers (>1) nor semiprimes. - M. F. Hasler, Jan 31 2008

MATHEMATICA

Select[Range[200], DivisorSigma[0, #] != PrimeOmega[#] + PrimeNu[#]&] (* Jean-Fran├žois Alcover, Jun 22 2018 *)

PROG

(Sage)

def is_A102467(n) :

    return bool(sloane.A001221(n) <> 1 and sloane.A001222(n) <> 2)

def A102467_list(n) :

    return [k for k in (1..n) if is_A102467(k)]

A102467_list(156)  # Peter Luschny, Feb 07 2012

(Haskell)

a102467 n = a102467_list !! (n-1)

a102467_list = [x | x <- [1..], a000005 x /= a001221 x + a001222 x]

-- Reinhard Zumkeller, Dec 14 2012

(PARI) is(n)=my(f=factor(n)[, 2]); #f!=1 && f!=[1, 1]~ \\ Charles R Greathouse IV, Oct 19 2015

CROSSREFS

Cf. A135767.

Sequence in context: A271345 A007624 A036456 * A126706 A123711 A200511

Adjacent sequences:  A102464 A102465 A102466 * A102468 A102469 A102470

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jan 09 2005

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 November 20 12:13 EST 2019. Contains 329335 sequences. (Running on oeis4.)