A230482 a(n) = (prime(prime(2*n)) - prime(2*prime(n)))/2.

-1, 2, 6, 12, 15, 28, 26, 39, 42, 41, 54, 44, 63, 72, 63, 81, 75, 102, 105, 105, 124, 121, 117, 174, 133, 134, 160, 181, 190, 197, 152, 198, 170, 240, 189, 210, 233, 243, 238, 232, 249, 289, 238, 283, 296, 339, 300, 228, 262, 330, 357, 371, 384, 378, 372

Offset: 1

Author

M. F. Hasler, Oct 20 2013

Keywords

• sign

Comments

As difference of two odd primes, all terms of A230481(n) = prime(prime(2*n))-prime(2*prime(n)) are even, which motivates to define the present sequence.

Further values: a(100)=617, a(10^3)=9344, a(10^4)=114171, a(10^5)=1325772, a(10^6)=14979156; a(10^10)~2.2*10^11, a(10^20)~3.9*10^21, a(10^30)~5.5*10^31.

Links

• M. F. Hasler, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A066066, A000040, A006450, A031215, A217622, A230460.

Programs

PARI

a=n->(prime(prime(2*n))-prime(2*prime(n)))/2

Formula

a(n) = (A217622(n) - A230460(n))/2.