A220851 a(n+1) is equal to a(n) plus the number of primes between a(n) and 2*a(n) exclusively.

2, 3, 4, 6, 8, 10, 14, 17, 21, 26, 32, 39, 48, 57, 71, 85, 101, 121, 144, 171, 200, 232, 272, 314, 363, 419, 483, 553, 637, 727, 829, 944, 1073, 1217, 1378, 1560, 1758, 1975, 2225, 2498, 2799, 3130, 3498, 3909, 4357, 4848, 5394, 5996, 6651, 7374, 8163

Offset

1,1

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

Crossrefs

Cf. A060715, A220850, inspired by A084140.

Sequence in context: A337046 A341031 A243225 * A028290 A003107 A217123

Adjacent sequences: A220848 A220849 A220850 * A220852 A220853 A220854

Keyword

easy,nonn

Author

Robert G. Wilson v, Dec 22 2012

Status

approved