A221943 - OEIS

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

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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