A117092 - OEIS

A117092

Numbers n such that nextprime(2*n) > 2*nextprime(n) (here nextprime = A007918; if p is prime then nextprime(p) = p).

2, 3, 4, 5, 7, 10, 11, 12, 13, 16, 17, 19, 22, 23, 27, 28, 29, 31, 37, 40, 41, 42, 43, 45, 46, 47, 52, 53, 57, 58, 59, 60, 61, 66, 67, 70, 71, 72, 73, 79, 82, 83, 87, 88, 89, 97, 100, 101, 102, 103, 106, 107, 108, 109, 112, 113, 126, 127, 129, 130, 131, 136

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OFFSET

1,1

COMMENTS

Contains all primes (A000040), and the intersection of A006093 and A047845. - Robert Israel, Mar 30 2016

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..10000

EXAMPLE

nextprime(2*12)=29 and nextprime(2)*nextprime(12)=2*13 then 12 is member because 29>26.

MAPLE

select(t -> nextprime(2*t) > 2*nextprime(t-1), [$1..100]); # Robert Israel, Mar 30 2016

MATHEMATICA

Select[Range@100, NextPrime[2 #] > 2 NextPrime[# - 1] &] (* Ivan Neretin, Mar 30 2016 *)

PROG

(PARI) for(i=1, 100, if(nextprime(2*i)<nextprime(2)*nextprime(i), print1(i, ", ")))

CROSSREFS

Cf. A000040, A006093, A007918, A047845.

Sequence in context: A254318 A047502 A356311 * A373255 A285276 A002504

Adjacent sequences: A117089 A117090 A117091 * A117093 A117094 A117095

KEYWORD

easy,nonn

AUTHOR

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

EXTENSIONS

Corrected by T. D. Noe, Oct 25 2006

STATUS

approved