|
| |
|
|
A065771
|
|
Prime powers n such that both tau[n^2] and sigma[n^2] are composite numbers.
|
|
1
| |
|
|
16, 81, 128, 625, 1024, 2187, 2401, 4096, 8192, 14641, 28561, 59049, 65536, 78125, 83521, 130321, 131072, 279841, 524288, 531441, 707281, 823543, 923521, 1594323, 1874161, 2825761, 3418801, 4194304, 4879681, 7890481, 9765625
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
FORMULA
| A000005[A025475(n)^2] and A000203[A025475(n)^2] are composite numbers.
|
|
|
MATHEMATICA
| Do[ s=DivisorSigma[ 0, n^2 ]; y=DivisorSigma[ 1, n^2 ]; If[ Equal[ Length[ FactorInteger[ n ] ], 1 ]&&!PrimeQ[ n ] &&!PrimeQ[ s ]&&!PrimeQ[ y ], Print[ n ] ], {n, 1, 10000000} ]
|
|
|
CROSSREFS
| Cf. A000005, A000203, A065403-A065405, A028982, A025475
Sequence in context: A110892 A202880 A088040 * A041490 A096020 A016898
Adjacent sequences: A065768 A065769 A065770 * A065772 A065773 A065774
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Nov 19 2001
|
| |
|
|
