A073721 Numbers k such that primepi(k) divides sigma(k).

2, 3, 5, 6, 7, 14, 15, 21, 29, 38, 44, 57, 66, 78, 92, 94, 95, 106, 108, 114, 116, 118, 120, 133, 154, 174, 177, 182, 188, 232, 255, 300, 304, 305, 349, 351, 359, 413, 417, 418, 468, 488, 506, 526, 595, 615, 629, 688, 872, 945, 954, 1001, 1002, 1006, 1011, 1018

Offset

1,1

Links

Table of n, a(n) for n=1..56.

Formula

{k : A000203(k)/A000720(k) is an integer}.

Mathematica

Do[s=Mod[DivisorSigma[1, n], PrimePi[n]]; If[s==0, Print[n]], {n, 1, 2500}]
Select[Range[2, 1200], Divisible[DivisorSigma[1, #], PrimePi[#]]&] (* Harvey P. Dale, Jan 31 2014 *)

Crossrefs

Cf. A000203, A000720, A073722-A073724.

Sequence in context: A057924 A103538 A144671 * A285639 A090745 A002229

Adjacent sequences: A073718 A073719 A073720 * A073722 A073723 A073724

Keyword

nonn

Author

Labos Elemer, Aug 05 2002

Status

approved