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A258934 Half the difference between the 2n-th prime and the n-th prime, starting from n=2. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

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

LINKS

Table of n, a(n) for n=2..60.

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

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Last modified June 17 22:17 EDT 2019. Contains 324200 sequences. (Running on oeis4.)