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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
OFFSET
1,2
COMMENTS
Numbers k such that sigma(k) is divisible by all proper divisors of k.
LINKS
FORMULA
{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
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Oct 06 2009, Oct 16 2009
STATUS
approved