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!)
A125191 Primes of the form k# + (k+1)# +- 1, where k# = A002110(k) = primorial(k). 2
2, 7, 37, 239, 241, 2521, 32341, 540539, 540541, 232792559, 232792561, 207030183359, 311671001662019, 41287621429375723111588738861, 5801527386969669153864265802424086050777441586253956297278498679 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Prime numbers n such that n = (prime(k+1) + 1)*k# +- 1 for some k.

LINKS

Table of n, a(n) for n=1..15.

EXAMPLE

Let k = 1; then 1#+2# = 2+6 = 8, 8-1 = 7 is prime but 8+1 = 9 is nonprime.

Let k = 3; then 3#+4# = 30+210 = 240, 240-1 = 239 is prime and 240+1 = 241 is also prime.

MAPLE

A002110 := 1 : A000040 := 2 : for n from 1 to 38 do if isprime(A002110*(1+A000040)-1) then printf("%d, ", A002110*(1+A000040)-1) ; fi ; if isprime(A002110*(1+A000040)+1) then printf("%d, ", A002110*(1+A000040)+1) ; fi ; A002110 := A002110*A000040 : A000040 := nextprime(A000040) : od : # R. J. Mathar, Jan 26 2007

PROG

(PARI) {m=37; for(n=0, m, p=primorial(n)+primorial(n+1); if(isprime(a=p-1), print1(a, ", ")); if(isprime(a=p+1), print1(a, ", ")))} \\ Klaus Brockhaus, Jan 25 2007

CROSSREFS

Cf. A002110 (primorial numbers), A006862 (Euclid numbers), A057588 (Kummer numbers).

Sequence in context: A245902 A063766 A020040 * A300559 A302859 A135164

Adjacent sequences:  A125188 A125189 A125190 * A125192 A125193 A125194

KEYWORD

nonn

AUTHOR

Tomas Xordan, Jan 12 2007

EXTENSIONS

Edited, corrected and extended by Klaus Brockhaus and R. J. Mathar, Jan 25 2007

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 February 19 04:07 EST 2020. Contains 332036 sequences. (Running on oeis4.)