A117096 Numbers n such that nextprime(2*n)<2*nextprime(n) (if p is prime then nextprime(p)=p).

1, 6, 8, 9, 14, 15, 18, 20, 21, 24, 25, 26, 30, 32, 33, 34, 35, 36, 38, 39, 44, 48, 49, 50, 51, 54, 55, 56, 62, 63, 64, 65, 68, 69, 74, 75, 76, 77, 78, 80, 81, 84, 85, 86, 90, 91, 92, 93, 94, 95, 96, 98, 99, 104, 105, 110, 111, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123

Offset

1,2

Comments

if p is prime and nextprime(p*n)<nextprime(p)*nextprime(n) then n is composite

Links

Table of n, a(n) for n=1..67.

Example

nextprime(2*6)=13 and nextprime(2)*nextprime(6)=2*7=14 then 6 is member because 13<14

Prog

(PARI) for(i=1, 150, if(nextprime(2*i)<nextprime(2)*nextprime(i), print1(i, ", ")))

Crossrefs

Sequence in context: A304412 A161982 A285275 * A067812 A356312 A337543

Adjacent sequences: A117093 A117094 A117095 * A117097 A117098 A117099

Keyword

easy,nonn

Author

Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Apr 18 2006

Status

approved