This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A015819 Numbers k such that phi(k + 3) | sigma(k). 1
 3, 6, 7, 11, 15, 19, 21, 23, 27, 31, 33, 42, 43, 51, 57, 59, 62, 69, 70, 71, 77, 79, 83, 84, 87, 93, 103, 131, 139, 141, 159, 163, 165, 177, 187, 189, 191, 199, 211, 213, 223, 235, 237, 251, 267, 270, 271, 282, 285, 287, 297, 311, 315, 316, 321, 330, 331 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 MAPLE select(t -> (numtheory:-sigma(t)/numtheory:-phi(t+3))::integer, [\$1..1000]); # Robert Israel, Dec 13 2018 MATHEMATICA Select[Range[1000], Divisible[DivisorSigma[1, #], EulerPhi[3 + #]] &] (* David Nacin, Mar 01 2012 *) PROG (PARI) is(n)=sigma(n)%(eulerphi(n+3))==0 \\ Charles R Greathouse IV, Sep 25 2012 CROSSREFS Cf. A056097. Contains A092109. Sequence in context: A255053 A292762 A258233 * A298794 A181683 A084125 Adjacent sequences:  A015816 A015817 A015818 * A015820 A015821 A015822 KEYWORD nonn AUTHOR 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 June 24 17:58 EDT 2019. Contains 324330 sequences. (Running on oeis4.)