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

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A109669 Numbers n such that the sum of the digits of sigma(n)^phi(n) is divisible by n. 0
 1, 19, 126, 162, 231, 255, 717, 1611, 1897, 3231, 3735, 8692, 8774, 10676, 16903, 17299, 22194, 30845, 92049, 309546, 459780, 502302, 763755, 788379 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS No more terms < 58000. - Emeric Deutsch, Jul 25 2006 LINKS EXAMPLE The digits of sigma(3735)^phi(3735) sum to 33615 and 33615 is divisible by 3735, so 3735 is in the sequence. MAPLE with(numtheory): sd:=proc(n) local nn: nn:=convert(n, base, 10): add(nn[j], j=1..nops(nn)) end: a:=proc(n) if sd(sigma(n)^phi(n)) mod n = 0 then n else fi end: seq(a(n), n=1..2000); # Emeric Deutsch, Jul 25 2006 MATHEMATICA Do[s = DivisorSigma[1, n]^EulerPhi[n]; k = Plus @@ IntegerDigits[s]; If[Mod[k, n] == 0, Print[n]], {n, 1, 10^4}] Select[Range[100000], Divisible[Total[IntegerDigits[DivisorSigma[1, #]^ EulerPhi[ #]]], #]&] (* Harvey P. Dale, Jan 03 2012 *) CROSSREFS Sequence in context: A126487 A241965 A182193 * A164905 A142106 A078851 Adjacent sequences:  A109666 A109667 A109668 * A109670 A109671 A109672 KEYWORD base,more,nonn AUTHOR Ryan Propper, Aug 06 2005 EXTENSIONS More terms from Emeric Deutsch, Jul 25 2006 One more term (a(19)) from Harvey P. Dale, Jan 03 2012 a(20)-a(24) from Lars Blomberg, Dec 02 2016 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 5 09:45 EST 2021. Contains 349543 sequences. (Running on oeis4.)