|
Search: id:A134611
|
|
|
| A134611 |
|
Nonprime numbers such that the cube mean of their prime factors is an integer (where the cube mean of c and d is ((c^3+d^3)/2)^(1/3)). |
|
+0
13
|
|
| 1, 4, 8, 9, 16, 25, 27, 32, 49, 64, 81, 121, 125, 128, 169, 243, 256, 289, 343, 361, 512, 529, 625, 729, 841, 961, 1024, 1331, 1369, 1512, 1681, 1849, 2048, 2187, 2197, 2209, 2401, 2809, 3125, 3481, 3721, 4096, 4489, 4913, 5041, 5329, 6241, 6561, 6859, 6889
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
COMMENT
|
All perfect prime powers (A025475) are included.
|
|
EXAMPLE
|
a(5)=25, since 25=5*5 and ((5^3+5^3)/2)^(1/3)=5. a(29)=1512, since 1512=2*2*2*3*3*3*7 and
((3*2^3+3*3^3+7^3)/7)^(1/3)=64^(1/3)=4.
|
|
CROSSREFS
|
Cf. A001597, A025475, A134333, A134344, A134376.
Cf. A134600, A134602, A134605, A134608, A134617, A134619, A134621.
Sequence in context: A088949 A134600 A134601 this_sequence A134612 A025475 A125643
Adjacent sequences: A134608 A134609 A134610 this_sequence A134612 A134613 A134614
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Hieronymus Fischer (Hieronymus.Fischer(AT)gmx.de), Nov 11 2007
|
|
|
Search completed in 0.002 seconds
|
