A221943 Floor(sqrt(7*2^n)).

2, 3, 5, 7, 10, 14, 21, 29, 42, 59, 84, 119, 169, 239, 338, 478, 677, 957, 1354, 1915, 2709, 3831, 5418, 7662, 10836, 15325, 21673, 30651, 43347, 61303, 86695, 122606, 173391, 245213, 346783, 490426, 693567, 980853, 1387135, 1961706, 2774271, 3923412, 5548542, 7846824, 11097085, 15693648, 22194170, 31387297

Offset: 0

Author

N. J. A. Sloane, Feb 01 2013

Keywords

• nonn

Comments

Theorem 3 of Dubickas implies that infinitely many terms of this sequence are divisible by 2 or 3 (and hence infinitely many composites). - Charles R Greathouse IV, Feb 04 2016

References

• Artūras Dubickas, Prime and composite integers close to powers of a number, Monatsh. Math. 158:3 (2009), pp. 271-284.

Crossrefs

Cf. A017910, A017913, A017919, A114183, A221718, A221942-A221946.

Programs

Mathematica

Floor[Sqrt[7*2^Range[0,50]]] (* Harvey P. Dale, Apr 11 2018 *)

PARI

a(n)=sqrtint(7<Charles R Greathouse IV, Apr 18 2013