login
This site is supported by donations to The OEIS Foundation.

 

Logo

"Email this user" was broken Aug 14 to 9am Aug 16. If you sent someone a message in this period, please send it again.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A070996 Numbers n such that its sum of divisors and number of divisors are both triangular numbers. 1
1, 12, 45, 98, 116, 212, 356, 531, 668, 908, 909, 2036, 2192, 3425, 3548, 3771, 3871, 4076, 4500, 4689, 4779, 5625, 5636, 6212, 6224, 8012, 8108, 8361, 8469, 8800, 9725, 9819, 10916, 11828, 12060, 12593, 13388, 15200, 18068, 20144, 21212, 22393, 23481, 23612 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..1000

PROG

(PARI) c=0; for(n=1, 15891631, s=sigma(n); s2=2*s; r=sqrtint(s2); if(r*(r+1)<>s2, next); nd=numdiv(n); nd2=2*nd; r=sqrtint(nd2); if(r*(r+1)==nd2, c++; write("b070996.txt", c " " n))) /* Donovan Johnson, Mar 10 2013 */

CROSSREFS

Sequence in context: A194284 A009785 A135710 * A015237 A024223 A251720

Adjacent sequences:  A070993 A070994 A070995 * A070997 A070998 A070999

KEYWORD

nonn

AUTHOR

Jason Earls (zevi_35711(AT)yahoo.com), May 18 2002

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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified August 18 22:21 EDT 2017. Contains 290770 sequences.