A220850 a(n+1) is equal to a(n) plus the number of primes between a(n) and 2*a(n) inclusively.

1, 2, 4, 6, 8, 10, 14, 17, 22, 28, 35, 43, 53, 65, 78, 93, 111, 129, 153, 179, 210, 245, 285, 328, 381, 441, 508, 582, 668, 764, 870, 990, 1123, 1270, 1436, 1625, 1825, 2054, 2309, 2590, 2904, 3246, 3631, 4052, 4512, 5022, 5582, 6197, 6872, 7612, 8421, 9312

Offset

1,2

Links

Robert G. Wilson v, Table of n, a(n) for n = 1..558

Example

a(6) = the number of primes between a(5) and 2*a(5) plus a(5) = the number of primes [8, 16] + 8 = 2 + 8 = 10.

Mathematica

f[n_] := PrimePi[ 2n] - PrimePi[n - 1]; NestList[# +f@# &, 1, 50]

Crossrefs

Cf. A035250, A220851, inspired by A084140.

Sequence in context: A367586 A242418 A191146 * A151566 A160406 A113293

Adjacent sequences: A220847 A220848 A220849 * A220851 A220852 A220853

Keyword

easy,nonn

Author

Robert G. Wilson v, Dec 22 2012

Status

approved