|
Search: id:A117520
|
|
|
| A117520 |
|
Triangular numbers for which the digital root is also a triangular number. |
|
+0
1
|
|
| 0, 1, 3, 6, 10, 15, 21, 28, 55, 66, 78, 91, 105, 120, 136, 190, 210, 231, 253, 276, 300, 325, 406, 435, 465, 496, 528, 561, 595, 703, 741, 780, 820, 861, 903, 946, 1081, 1128, 1176, 1225, 1275, 1326, 1378, 1540, 1596, 1653, 1711, 1770, 1830, 1891, 2080, 2145
(list; graph; listen)
|
|
|
OFFSET
|
1,3
|
|
|
COMMENT
|
All triangular numbers have a digital root of 1,3,6 or 9 (except for the number 0). So this sequence contains all triangular numbers except those which have digital root 9.
|
|
EXAMPLE
|
2926 is in the sequence because (1) it is a triangular number, and (2) the digital root is 1, which is a triangular number.
|
|
CROSSREFS
|
Cf. A000217.
Sequence in context: A025706 A025730 A066353 this_sequence A062099 A115650 A025745
Adjacent sequences: A117517 A117518 A117519 this_sequence A117521 A117522 A117523
|
|
KEYWORD
|
easy,nonn,base
|
|
AUTHOR
|
Luc Stevens (lms022(AT)yahoo.com), Apr 28 2006
|
|
|
Search completed in 0.002 seconds
|
