|
Search: id:A073716
|
|
|
| A073716 |
|
Numbers n such that the number of prime divisors of n (counted with multiplicity) = number of anti-divisors of n. |
|
+0
1
|
|
| 1, 3, 9, 20, 30, 40, 44, 80, 84, 100, 114, 168, 174, 192, 208, 244, 256, 272, 300, 316, 324, 404, 440, 456, 464, 520, 524, 596, 672, 704, 720, 834, 894, 1044, 1064, 1248, 1272, 1324, 1416, 1464, 1604, 1608, 1626, 1632, 1636, 1680, 1686, 1704, 1744, 1756
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
COMMENT
|
See A066272 for definition of anti-divisor.
|
|
EXAMPLE
|
40 is a term since its prime factors are {2, 2, 2, 5} and its anti-divisors are {3, 9, 16, 27}.
|
|
PROGRAM
|
(PARI) {for(n=1, 1800, v1=[]; v2=[]; v3=[]; ds=divisors(2*n-1); for(k=2, matsize(ds)[2]-1, if(ds[k]%2>0, v1=concat(v1, ds[k]))); ds=divisors(2*n); for(k=2, matsize(ds)[2]-1, if(ds[k]%2>0, v2=concat(v2, ds[k]))); ds=divisors(2*n+1); for(k=2, matsize(ds)[2]-1, if(ds[k]%2>0, v3=concat(v3, ds[k]))); v=vecsort(concat(v1, concat(v2, v3))); if(matsize(v)[2]==bigomega(n), print1(n, ", ")))}
|
|
CROSSREFS
|
Cf. A001222, A066272.
Sequence in context: A146066 A164283 A033315 this_sequence A037048 A139142 A037257
Adjacent sequences: A073713 A073714 A073715 this_sequence A073717 A073718 A073719
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Jason Earls (zevi_35711(AT)yahoo.com), Aug 30 2002
|
|
EXTENSIONS
|
Edited and extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Sep 02 2002
|
|
|
Search completed in 0.002 seconds
|
