login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A086125 Values of n such that f(n) is a prime, where f(1) = 1, f(n) = prime(n)*f(n-1) + 2. 0
2, 4, 8, 15, 31, 128, 163 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

No additional terms up to n = 1000. - Harvey P. Dale, Feb 02 2019

LINKS

Table of n, a(n) for n=1..7.

MATHEMATICA

f[1]=1; f[x_] := f[x] = Prime[x]*f[x - 1] + 2; Do[ If[ PrimeQ[ f[n]], Print[n]], {n, 1, 1900}]

nxt[{n_, a_}]:={n+1, a*Prime[n+1]+2}; Select[NestList[nxt, {1, 1}, 200], PrimeQ[ #[[2]]]&][[All, 1]] (* Harvey P. Dale, Feb 02 2019 *)

CROSSREFS

The primes are in A086124.

Cf. A000668, A076481, A086122, A086123, A086124.

Sequence in context: A092603 A298533 A259805 * A227236 A061030 A036661

Adjacent sequences: A086122 A086123 A086124 * A086126 A086127 A086128

KEYWORD

more,nonn

AUTHOR

Labos Elemer, Jul 23 2003

EXTENSIONS

Edited by Robert G. Wilson v, Jul 25 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 27 11:37 EST 2022. Contains 358405 sequences. (Running on oeis4.)