A258934 Half the difference between the 2n-th prime and the n-th prime, starting from n=2.

2, 4, 6, 9, 12, 13, 17, 19, 21, 24, 26, 30, 32, 33, 39, 40, 45, 48, 51, 54, 57, 58, 67, 66, 69, 74, 78, 81, 84, 83, 90, 90, 99, 100, 104, 108, 110, 115, 118, 121, 126, 126, 132, 133, 140, 140, 140, 147, 156, 162, 165, 168, 171, 172, 175, 175, 185, 185, 189

Offset

2,1

Comments

The differences between odd prime numbers are always even, so a(n) is well defined for n>=2.

Links

Seiichi Manyama, Table of n, a(n) for n = 2..10000

Formula

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

a(n) = A072473(n)/2.

Mathematica

Table[(Prime[2 k] - Prime[k])/2, {k, 2, 60}]

Prog

(Sage) [(nth_prime(2*n)-nth_prime(n))/2 for n in (2..60)] # Bruno Berselli, Jun 15 2015
(Magma) [(NthPrime(2*n)-NthPrime(n))/2: n in [2..60]]; // Bruno Berselli, Jun 15 2015

Crossrefs

Cf. A072473, A072715, A087461.

Sequence in context: A220768 A077220 A128716 * A225600 A183422 A025057

Adjacent sequences: A258931 A258932 A258933 * A258935 A258936 A258937

Keyword

nonn,easy

Author

Federico Provvedi, Jun 15 2015

Status

approved