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!)
A221491 Number of primes of the form k*n - k + n, 1 <= k <= n. 3
0, 1, 2, 2, 2, 2, 5, 2, 3, 3, 5, 3, 6, 4, 7, 6, 5, 4, 9, 2, 8, 7, 8, 4, 11, 5, 10, 8, 10, 4, 16, 3, 10, 10, 12, 9, 15, 4, 10, 11, 13, 6, 20, 7, 11, 10, 15, 8, 19, 6, 19, 13, 16, 5, 25, 10, 19, 10, 15, 9, 26, 7, 16, 13, 16, 13, 30, 9, 18, 14, 26, 10, 25, 10 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) = sum(A010051(A162610(n,k)): k=1..n) = number of primes in n-th row of the triangle in A162610. - Reinhard Zumkeller, Jan 19 2013

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

EXAMPLE

Row 10 of A162610 = [19,28,37,46,55,64,73,82,91,100] containing three primes: [19,37,73], therefore a(10) = 3;

row 11 of A162610 = [21,31,41,51,61,71,81,91,101,111,121] containing five primes: [31,41,61,71,101], therefore a(11) = 5.

PROG

(Haskell)

a221491 n = sum [a010051' (k*n - k + n) | k <- [1..n]]

CROSSREFS

Cf. A221490.

Sequence in context: A123487 A130325 A154097 * A224254 A107604 A080647

Adjacent sequences:  A221488 A221489 A221490 * A221492 A221493 A221494

KEYWORD

nonn,tabl

AUTHOR

Reinhard Zumkeller, Jan 19 2013

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 May 31 07:09 EDT 2020. Contains 334747 sequences. (Running on oeis4.)