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

0,1

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.

Links

Table of n, a(n) for n=0..47.

Mathematica

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

Prog

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

Crossrefs

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

Sequence in context: A241550 A319564 A347869 * A120446 A082531 A291298

Adjacent sequences: A221940 A221941 A221942 * A221944 A221945 A221946

Keyword

nonn

Author

N. J. A. Sloane, Feb 01 2013

Status

approved