A137371 - OEIS

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A137371

a(n) = least semiprime such that all subsets of {a(1),...,a(n)} have a different sum.

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

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..29.

S. J. Benkoski and P. Erdős, On weird and pseudoperfect numbers, Math. Comp., 28 (1974), pp. 617-623. Alternate link; 1975 corrigendum

MAPLE

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: # R. J. Mathar

CROSSREFS

Cf. A001358, A006037, A064934.

Sequence in context: A118692 A020706 A226271 * A179463 A086697 A372533

Adjacent sequences: A137368 A137369 A137370 * A137372 A137373 A137374

KEYWORD

more,nonn

AUTHOR

Jonathan Vos Post, Apr 09 2008

EXTENSIONS

More terms from R. J. Mathar

a(12)-a(29) from Donovan Johnson, Nov 11 2008

STATUS

approved