A166070 Sorted sequence of primes and multiply perfect numbers.

1, 2, 3, 5, 6, 7, 11, 13, 17, 19, 23, 28, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 120, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263

Offset

1,2

Comments

Numbers k such that sigma(k) is divisible by all proper divisors of k.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

A000040 Union A007691.

{1} Union A053813 Union A166069.

{1} Union A000040 Union A000396 Union A166069.

Example

a(4) = 6: all proper divisors of 6 (1, 2, 3) divide sigma(6) = 12.

Mathematica

Select[Range[300], And@@Divisible[DivisorSigma[1, #], Most[Divisors[#]]]&] (* Harvey P. Dale, Jan 18 2015 *)

Crossrefs

Cf. A053813.

Sequence in context: A352936 A340076 A340150 * A053813 A116974 A031402

Adjacent sequences: A166067 A166068 A166069 * A166071 A166072 A166073

Keyword

nonn

Author

Jaroslav Krizek, Oct 06 2009, Oct 16 2009

Status

approved