login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A247604 Least integer m > 0 with pi(m*n) = sigma(m+n), where pi(.) and sigma(.) are given by A000720 and A000203. 7
18, 11, 360, 251, 168, 36, 6, 285, 1185, 792, 29, 11, 245078, 5, 1869, 46074, 573, 42863, 11, 5, 8129, 60806, 1443, 452, 15, 39298437, 386891, 1041920, 1290489, 17630, 35569, 10, 8174777, 3152500, 4291325, 57880072, 55991485, 127358, 93462807, 93314912 (list; graph; refs; listen; history; text; internal format)
OFFSET

5,1

COMMENTS

Conjecture: a(n) exists for every n = 5,6,...

LINKS

Zhi-Wei Sun and Hiroaki Yamanouchi, Table of n, a(n) for n = 5..52 (terms a(5)-a(40) from Zhi-Wei Sun)

Zhi-Wei Sun, A new theorem on the prime-counting function, arXiv:1409.5685, 2014.

EXAMPLE

a(5) = 18 since pi(5*18) = 24 = sigma(5+18).

MATHEMATICA

Do[m=1; Label[aa]; If[PrimePi[n*m]==DivisorSigma[1, m+n], Print[n, " ", m]; Goto[bb]]; m=m+1; Goto[aa];

Label[bb]; Continue, {n, 5, 40}]

CROSSREFS

Cf. A000203, A000720, A247600, A247601, A247602, A247603, A247672, A247673.

Sequence in context: A244093 A195926 A195929 * A194659 A194186 A033668

Adjacent sequences:  A247601 A247602 A247603 * A247605 A247606 A247607

KEYWORD

nonn

AUTHOR

Zhi-Wei Sun, Sep 21 2014

EXTENSIONS

a(41)-a(44) 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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 3 23:57 EDT 2020. Contains 334808 sequences. (Running on oeis4.)