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Search: id:A137371
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| A137371 |
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a(n) = least semiprime such that all subsets of {a(1),...,a(n)} have a different sum. |
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+0
1
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| 4, 6, 9, 14, 22, 57, 111, 218, 445, 879, 1754, 3518, 7034, 14069, 28129, 56271, 112529, 225073, 450139, 900274, 1800559, 3601109, 7202221, 14404439, 28808881, 57617759, 115235531, 230471069, 460942121
(list; graph; listen)
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OFFSET
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1,1
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REFERENCES
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J. Stanley Benkoski and P. Erdos, On weird and pseudoperfect numbers, Math. Comp. 28, no. 126, 617-623, 1974.
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MAPLE
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isA001358 := proc(n) if numtheory[bigomega](n) = 2 then true; else false; fi ; end: setsum := proc(S) add(i, i=S) ; end: a := [4] : while true do for anxt from op(-1, a)+1 do if isA001358(anxt) then aset := combinat[powerset](convert(a, set) union {anxt} ); sset := {} ; for s in aset do sset := sset union { setsum(s) } ; od: if nops(sset) = nops(aset) then a := [op(a), anxt] ; print(a) ; break ; fi ; fi ; od: od:
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CROSSREFS
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Cf. A001358, A006037, A064934.
Adjacent sequences: A137368 A137369 A137370 this_sequence A137372 A137373 A137374
Sequence in context: A118689 A118692 A020706 this_sequence A086697 A078443 A085751
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KEYWORD
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easy,more,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Apr 09 2008
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EXTENSIONS
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Maple code and extension from R. J. Mathar (mathar(AT)strw.leidenuniv.nl)
a(12)-a(29) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Nov 11 2008
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