login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A061285 a(n) = 2^((prime(n) - 1)/2). 2
2, 4, 8, 32, 64, 256, 512, 2048, 16384, 32768, 262144, 1048576, 2097152, 8388608, 67108864, 536870912, 1073741824, 8589934592, 34359738368, 68719476736, 549755813888, 2199023255552, 17592186044416, 281474976710656 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

Square root of 2^(prime(n) - 1), i.e., the smallest number that has prime(n) divisors.

LINKS

Table of n, a(n) for n=2..25.

Index to divisibility sequences

FORMULA

a(n) = sqrt(min(x; A000005(x) = prime(n))) = sqrt(A034785(n)/2) = sqrt(2^(prime(n) - 1)) = sqrt(2^A006093(n)) = sqrt(2^phi(prime(n))) = sqrt(2^A000010(A000040(n))).

Sum_{n>=1} 1/a(n) = A217054. - Amiram Eldar, Dec 23 2020

MATHEMATICA

Table[2^((Prime[n] - 1)/2), {n, 2, 25}] (* Amiram Eldar, Dec 23 2020 *)

CROSSREFS

Cf. A000005, A000010, A005097, A005179, A006005, A006093, A034785, A217054.

Sequence in context: A307611 A053147 A128055 * A194810 A271216 A102000

Adjacent sequences:  A061282 A061283 A061284 * A061286 A061287 A061288

KEYWORD

nonn

AUTHOR

Labos Elemer, May 22 2001

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 10 21:47 EDT 2021. Contains 342856 sequences. (Running on oeis4.)