This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A247672 Least integer m > 0 with pi(m*n) = phi(m) + phi(n), where pi(.) is the prime-counting function and phi(.) is Euler's totient function. 6
 6, 2, 2, 23, 3, 1, 3, 1033, 2, 6449, 15887, 1, 100169, 268393, 636917, 2113589, 70324093, 1, 27852457, 78848479, 2, 468329417, 4, 1, 10220118551 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Conjecture: a(n) exists for any n > 0. LINKS Zhi-Wei Sun, A new theorem on the prime-counting function, arXiv:1409.5685, 2014. EXAMPLE a(1) = 6 since pi(6) = 3 = phi(1) + phi(6), and pi(1*m) = phi(1) + phi(m) for no m < 6. MATHEMATICA Do[m=1; Label[aa]; If[PrimePi[m*n]==EulerPhi[m]+EulerPhi[n], Print[n, " ", m]; Goto[bb]]; m=m+1; Goto[aa]; Label[bb]; Continue, {n, 1, 18}] Table[m = 1; While[PrimePi[n*m] != EulerPhi[m] + EulerPhi[n], m++]; m, {n, 1, 12}] (* Robert Price, Sep 08 2019 *) CROSSREFS Cf. A000010, A000720, A247600, A247601, A247602, A247603, A247604, A247673. Sequence in context: A138995 A010133 A065280 * A188726 A272354 A196552 Adjacent sequences:  A247669 A247670 A247671 * A247673 A247674 A247675 KEYWORD nonn,more AUTHOR Zhi-Wei Sun, Sep 22 2014 EXTENSIONS a(19)-a(25) from Hiroaki Yamanouchi, Oct 04 2014 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 12 20:12 EST 2019. Contains 329961 sequences. (Running on oeis4.)