|
Search: id:A067787
|
|
|
| A067787 |
|
Numbers n such that the number of primes not exceeding sigma(n) equals phi(n), i.e. pi(sigma(n)) = phi(n). |
|
+0
1
|
| |
|
|
OFFSET
|
1,1
|
|
|
EXAMPLE
|
pi(sigma(9)) = pi(13) = 6 = phi(9).
|
|
MATHEMATICA
|
pi[n_] := Module[{i = 0}, While[Prime[i + 1] <= n, i++ ]; i]; Do[If[pi[DivisorSigma[1, n]] == EulerPhi[n], Print[n]], {n, 1, 10^4}]
|
|
CROSSREFS
|
Sequence in context: A085686 A084756 A009578 this_sequence A130491 A149013 A149014
Adjacent sequences: A067784 A067785 A067786 this_sequence A067788 A067789 A067790
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Feb 06 2002
|
|
|
Search completed in 0.002 seconds
|
