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Search: id:A109761
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| A109761 |
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A rare pseudoperfect (or semiperfect) number is a pseudoperfect number n such that n mod 12 is 2 or 10. There are 1232 pseudoperfect numbers less than or equal to 5000 but only 42 rare ones. |
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+0
1
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| 350, 490, 550, 650, 770, 910, 1190, 1330, 1430, 1610, 1750, 1870, 2002, 2030, 2090, 2170, 2210, 2450, 2470, 2530, 2590, 2750, 2870, 2990, 3010, 3190, 3230, 3250, 3290, 3410, 3430, 3710, 3770, 3850, 4070, 4130, 4270, 4510, 4550, 4690, 4730, 4970
(list; graph; listen)
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OFFSET
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1,1
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MAPLE
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with(combinat); issemiperfect := proc(n) local b, S; b:=false; S:=subsets(divisors(n) minus {n}); while not S[finished] do if convert(S[nextvalue](), `+`)=n then b:=true; break fi od; return b end: S:=remove(proc(z) type(z, odd) end, [$1..5000]): SP:=select(proc(z) issemiperfect(z) end, S): RSP:=select(proc(z) z mod 12 = 2 or z mod 12 = 10 end, SP);
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CROSSREFS
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Cf. A005835.
Sequence in context: A054824 A138944 A043619 this_sequence A109762 A074055 A108776
Adjacent sequences: A109758 A109759 A109760 this_sequence A109762 A109763 A109764
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KEYWORD
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nonn
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AUTHOR
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Walter A. Kehowski (wkehowski(AT)cox.net), Aug 12 2005
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