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A258934
Half the difference between the 2n-th prime and the n-th prime, starting from n=2.
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
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
KEYWORD
nonn,easy
AUTHOR
Federico Provvedi, Jun 15 2015
STATUS
approved