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A166070 Sorted sequence of primes and multiply perfect numbers. 4
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

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

For n = 4 the a(4) = 6, all proper divisors of 6 (1, 2, 3) divides 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: A325327 A003174 A238463 * A053813 A116974 A031402

Adjacent sequences:  A166067 A166068 A166069 * A166071 A166072 A166073

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Oct 06 2009, Oct 16 2009

STATUS

approved

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Last modified May 30 05:35 EDT 2020. Contains 334712 sequences. (Running on oeis4.)