A163587 A sequence of primes suggested by Ramanujan's: 2*n*log(2*n) < R(n) < 4*n*log(4*n) : floor((2n+m)* log(2*n+m)) if Prime.

5, 23, 29, 59, 307, 383, 449, 691, 727, 739, 751, 787, 947, 971, 1009, 1021, 1097, 1237, 1289, 1367, 1511, 1657, 1697, 1913, 2063, 2243, 2579, 2593, 2621, 2749, 2777, 2791, 2963, 3049, 3121, 3251, 3499, 3617, 3631, 3779, 3793, 3823

Offset

1,1

Comments

The result is not A104272, but seems to be distantly related. Duplicates are discarded by the Union[].

Links

G. C. Greubel, Table of n, a(n) for n = 1..1000

J. Sondow, Ramanujan primes and Bertrand's postulate, Amer. Math. Monthly 116 (2009) 630-635.

Formula

If floor((2n+m)* log(2*n+m)) is prime, then floor((2n+m)* log(2*n+m)).

Mathematica

a[n_] = Floor[2*n*Log[2*n]]; Table[Table[If[PrimeQ[a[n + m]], a[n + m], {}], {m, 0, 2*n}], {n, 1, 100}]; Union[Flatten[%]]

Crossrefs

Cf. A104272.

Sequence in context: A067367 A140386 A105880 * A038922 A019367 A065867

Adjacent sequences: A163584 A163585 A163586 * A163588 A163589 A163590

Keyword

nonn,uned

Author

Roger L. Bagula, Jul 31 2009

Status

approved