|
| |
|
|
A073703
|
|
Smallest prime p such that also p+prime(n)*2 is a prime.
|
|
16
| |
|
|
3, 5, 3, 3, 7, 3, 3, 3, 7, 3, 5, 5, 7, 3, 3, 3, 13, 5, 3, 7, 3, 5, 7, 3, 3, 31, 5, 13, 5, 3, 3, 7, 3, 3, 13, 5, 3, 5, 3, 3, 31, 5, 7, 3, 3, 3, 11, 3, 3, 3, 13, 13, 5, 7, 7, 31, 3, 5, 3, 7, 3, 7, 3, 19, 5, 7, 11, 3, 7, 3, 3, 43, 5, 5, 3, 3, 19, 3, 7, 3, 19, 11, 19, 11, 3, 43, 13, 5, 7, 3, 3, 13, 3
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| If Polignac's conjecture (1849) is correct, the sequence is defined for all n (as is A020483).
Also: least k-prime(n) such that k-prime(n) and k+prime(n) are both primes. - Pierre CAMI (pierre-cami(AT)bbox.fr), Aug 27 2004
|
|
|
LINKS
| Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
|
|
|
EXAMPLE
| n=5: prime(5)=11; 2+11*2=24, 3+11*2=25 and 5+11*2=27 are not prime, but 7+11*2=29 is prime, therefore a(5)=7.
|
|
|
MATHEMATICA
| f[n_] := Block[{k = Prime[n], p = Prime[n]}, While[ !PrimeQ[k - p] || !PrimeQ[k + p], k++ ]; k - p]; Table[ f[n], {n, 95}] (from Robert G. Wilson v Aug 28 2004)
|
|
|
PROG
| (PARI) forprime(q=2, 500, forprime(p=2, default(primelimit), if(isprime(2*q+p), print1(p", "); next(2))); error("Not enough precomputed primes")) \\ Charles R Greathouse IV, Aug 21 2011
|
|
|
CROSSREFS
| Cf. A073704, A001747, A000040, A020483.
Sequence in context: A021287 A124887 A097524 * A175019 A097519 A133773
Adjacent sequences: A073700 A073701 A073702 * A073704 A073705 A073706
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 04 2002
|
|
|
EXTENSIONS
| Merged with Pierre CAMI's submission of Aug 2004 - R. J. Mathar Jul 29 2008
|
| |
|
|
