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

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A079951 Number of primes p with prime(n) == 1 (modulo 2*p). 2
0, 0, 1, 1, 1, 2, 1, 1, 1, 2, 2, 2, 2, 2, 1, 2, 1, 3, 2, 2, 2, 2, 1, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 1, 1, 2, 1, 3, 2, 2, 2, 2, 3, 2, 1, 3, 2, 2, 3, 1, 1, 1, 2, 2, 3, 3, 2, 2, 2, 2, 3, 2, 3, 3, 1, 3, 2, 1, 2, 3, 2, 1, 2, 3, 2, 3, 2, 4, 2, 2, 2, 2, 2, 3, 3, 3, 1, 1, 1, 2, 2, 1, 2, 3, 2, 3, 3, 2, 1, 2, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Table of n, a(n) for n=1..105.

FORMULA

a(n) = A001221(floor(A000040(n)/2)). - Jon Maiga, Jan 06 2019

EXAMPLE

n=6: prime(6)=13 and 13 mod (2*2) = 1, 13 mod (2*3) = 1, 13 mod(2*5) = 3, 13 mod (2*7) = 13, therefore a(6)=2.

MATHEMATICA

Table[PrimeNu[Floor[Prime[n]/2]], {n, 105}] (* Jon Maiga, Jan 06 2019 *)

PROG

(PARI) a(n) = omega(prime(n)\2); \\ Michel Marcus, Jan 06 2019

CROSSREFS

Cf. A001221, A079950, A079952.

Sequence in context: A086288 A104360 A318998 * A095407 A038605 A113121

Adjacent sequences:  A079948 A079949 A079950 * A079952 A079953 A079954

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jan 19 2003

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 January 19 03:18 EST 2020. Contains 331031 sequences. (Running on oeis4.)