|
Search: id:A107816
|
|
| |
|
| 1, 8, 20, 48, 144, 240, 720, 480, 756, 720, 864, 2304, 2880, 4080, 5040, 6240, 6048, 6720, 9984, 21600, 90720, 506880, 806400, 748800, 973440, 1153152
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
COMMENT
|
Numbers n such that n = sigma(k) = phi(prime(k)-1) for some k.
Values of k are in A067651, values of prime(k) are in A107815.
|
|
EXAMPLE
|
a(3) = sigma(A067651(3)) = sigma(19) = 20.
|
|
PROGRAM
|
(PARI) m=400000; for(n=1, m, s=sigma(n); if(s==eulerphi(prime(n)-1), print1(s, ", ")))
|
|
CROSSREFS
|
Cf. A067651, A107815.
Sequence in context: A006416 A121307 A086169 this_sequence A036835 A101363 A003685
Adjacent sequences: A107813 A107814 A107815 this_sequence A107817 A107818 A107819
|
|
KEYWORD
|
nonn,more
|
|
AUTHOR
|
Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), May 24 2005
|
|
|
Search completed in 0.002 seconds
|
