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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A319273 Signed sum over the prime multiplicities of n. 2
1, 1, 1, 2, 1, 0, 1, 3, 2, 0, 1, 1, 1, 0, 0, 4, 1, -1, 1, 1, 0, 0, 1, 2, 2, 0, 3, 1, 1, 1, 1, 5, 0, 0, 0, 0, 1, 0, 0, 2, 1, 1, 1, 1, 1, 0, 1, 3, 2, -1, 0, 1, 1, -2, 0, 2, 0, 0, 1, 2, 1, 0, 1, 6, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, -1, 1, 0, 1, 1, 3, 4, 0, 1, 2, 0, 0, 0, 2, 1, 0, 0, 1, 0, 0, 0, 4, 1, -1, 1, 0, 1, 1, 1, 2, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

If n = Product prime(x_i)^y_i is the prime factorization of n, then a(n) = Sum (-1)^(i-1) y_i.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

EXAMPLE

The prime factorization of 810 is 2^1 * 3^4 * 5^1, so a(810) = 1 - 4 + 1 = -2.

MATHEMATICA

Table[Total[MapIndexed[(-1)^(#2[[1]]-1)*#1&, Last/@FactorInteger[n]]], {n, 100}]

PROG

(PARI) A319273(n) = if(1==n, n, my(f=factor(n)); sum(i=1, #f~, f[i, 2] * ((-1)^(i-1)))); \\ Antti Karttunen, Sep 30 2018

CROSSREFS

Cf. A000040, A001221, A001222, A008683, A071321, A195017, A268387, A316523, A316524.

Sequence in context: A292131 A255740 A100995 * A272894 A268387 A136566

Adjacent sequences:  A319270 A319271 A319272 * A319274 A319275 A319276

KEYWORD

sign

AUTHOR

Gus Wiseman, Sep 16 2018

EXTENSIONS

More terms from Antti Karttunen, Sep 30 2018

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 September 15 18:22 EDT 2019. Contains 327082 sequences. (Running on oeis4.)