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

 

Logo

Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A077510 Numbers n such that n + pi(n) is a prime. 5
2, 3, 7, 9, 12, 13, 21, 28, 32, 36, 45, 52, 55, 57, 61, 65, 70, 76, 79, 81, 84, 86, 89, 101, 104, 110, 119, 121, 131, 135, 139, 145, 147, 155, 160, 162, 172, 181, 185, 187, 195, 205, 216, 222, 223, 228, 231, 253, 258, 262, 273, 278, 286, 288, 292, 297, 305, 310 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Conjecture: for k > 5, prime(n) = < k < prime(n+1) <= k + Pi(k), i.e. the smallest prime greater than k is <= k +Pi(k). Equality holds for k = 7.

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

21 is a member as 21 + pi(21) = 21 + 8 = 29 is a prime.

MATHEMATICA

Select[Range[350], PrimeQ[#+PrimePi[#]]&] (* Harvey P. Dale, Nov 19 2011 *)

PROG

(PARI) for(n=1, 200, if(isprime(n+primepi(n)), print1(n, ", "))) \\ Derek Orr, Jun 22 2015

(PARI) pi=0; p=2; forprime(q=3, 1e3, pi++; for(n=p, q-1, if(isprime(n+pi), print1(n", "))); p=q) \\ Charles R Greathouse IV, Jun 23 2015

CROSSREFS

Cf. A061067, A076757.

Sequence in context: A103797 A262814 A260641 * A178433 A073148 A014839

Adjacent sequences:  A077507 A077508 A077509 * A077511 A077512 A077513

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Nov 08 2002

EXTENSIONS

More terms from David Garber, Nov 10 2002

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified November 19 04:03 EST 2017. Contains 294912 sequences.