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 A015849 Numbers n such that phi(n + 9) | sigma(n) for n not congruent to 0 (mod 3). 2
 5, 7, 10, 31, 47, 79, 127, 145, 161, 223, 238, 239, 355, 367, 371, 376, 418, 455, 463, 479, 748, 863, 1039, 1045, 1087, 1103, 1118, 1327, 1423, 1439, 1567, 1583, 1823, 1886, 1999, 2065, 2108, 2143, 2201, 2207, 2239, 2447, 2461, 2687, 2767, 2840, 2927, 2975 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Includes primes p such that (p+9)/8 is prime. Thus Dickson's conjecture implies the sequence is infinite. - Robert Israel, Jan 10 2019 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 MAPLE select(n -> (numtheory:-sigma(n)/numtheory:-phi(n+9))::integer, [seq(seq(3*i+j, j=1..2), i=0..1000)]); # Robert Israel, Jan 10 2019 MATHEMATICA Select[Range[1, 5000], Divisible[DivisorSigma[1, #], EulerPhi[9 + #]] && ! Mod[#, 3] == 0 &] (* David Nacin, Mar 04 2012 *) PROG (PARI) is(n)=n%3 && sigma(n)%eulerphi(n+9)==0 \\ Charles R Greathouse IV, Sep 25 2012 CROSSREFS Cf. A015827. Sequence in context: A131998 A141443 A215660 * A059303 A061523 A119653 Adjacent sequences:  A015846 A015847 A015848 * A015850 A015851 A015852 KEYWORD nonn AUTHOR STATUS approved

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Last modified December 3 18:19 EST 2021. Contains 349467 sequences. (Running on oeis4.)