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!)
A189986 Numbers of the form 4k+1 having exactly 4 divisors. 1
21, 33, 57, 65, 69, 77, 85, 93, 125, 129, 133, 141, 145, 161, 177, 185, 201, 205, 209, 213, 217, 221, 237, 249, 253, 265, 301, 305, 309, 321, 329, 341, 365, 377, 381, 393, 413, 417, 437, 445, 453, 469, 473, 481, 485, 489, 493, 497, 501, 505, 517, 533, 537, 545 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Intersection of A016813 and A030513; subsequence of A007422.

Numbers p*q with p = q (mod 4) together with p^3 with p=1 (mod 4), p and q distinct primes. - Charles R Greathouse IV, May 03 2011

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..10000

MATHEMATICA

Select[4Range[200]+1, DivisorSigma[0, #]==4&] (* Harvey P. Dale, May 11 2011 *)

PROG

(MAGMA) [ n: n in [1..600 by 4] | #Divisors(n) eq 4 ]; // Klaus Brockhaus, May 04 2011

CROSSREFS

Cf. A007422, A016813, A030513.

Sequence in context: A330441 A176945 A070006 * A190299 A280262 A084109

Adjacent sequences:  A189983 A189984 A189985 * A189987 A189988 A189989

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, May 03 2011

EXTENSIONS

Corrected (497 inserted) by Klaus Brockhaus, May 04 2011

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 June 5 03:12 EDT 2020. Contains 334828 sequences. (Running on oeis4.)