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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A257567 a(n) = the highest power of 3 that divides (prime(n)^2+2). 2
1, 0, 3, 1, 1, 2, 1, 1, 2, 1, 2, 1, 2, 1, 1, 1, 4, 1, 2, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 3, 1, 2, 1, 2, 2, 1, 3, 1, 3, 1, 1, 1, 1, 2, 1, 1, 3, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 1, 1, 2, 2, 1, 2, 1, 1, 1, 2, 2, 1, 1, 1, 1, 3, 1, 4, 1, 1, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 2, 1, 2 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Except for n=2, all a(n)>1 because (prime(n)^2+2) is divisible by 3.

LINKS

Zak Seidov, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = A007949(A061725(n)). - Michel Marcus, May 01 2015

EXAMPLE

a(1) = 1 because p=prime(1)=2 and p^2+2 = 6 = 3^1*2,

a(2) = 0 because p=prime(2)=3 and p^2+2 = 11 = 3^0*11,

a(3) = 3 because p=prime(3)=5 and p^2+2 = 27 = 3^3.

MATHEMATICA

Table[IntegerExponent[Prime[k]^2 + 2, 3], {k, 100}]

PROG

(PARI) a(n) = valuation(prime(n)^2+2, 3); \\ Michel Marcus, May 01 2015

CROSSREFS

Cf. A007949 (3-adic valuation), A061725 (p^2+2, with p prime), A257568.

Sequence in context: A174820 A099501 A089762 * A318440 A189965 A258820

Adjacent sequences:  A257564 A257565 A257566 * A257568 A257569 A257570

KEYWORD

nonn

AUTHOR

Zak Seidov, Apr 30 2015

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 April 21 10:03 EDT 2019. Contains 322328 sequences. (Running on oeis4.)