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 A074753 Number of integers k such that sigma(k) < n. 7
 0, 1, 1, 2, 3, 3, 4, 5, 6, 6, 6, 6, 8, 9, 10, 11, 11, 11, 13, 13, 14, 14, 14, 14, 17, 17, 17, 17, 18, 18, 19, 21, 23, 23, 23, 23, 24, 24, 25, 26, 27, 27, 30, 30, 31, 31, 31, 31, 34, 34, 34, 34, 34, 34, 36, 36, 38, 39, 39, 39, 42, 42, 43, 44, 44, 44, 44, 44, 45, 45, 45, 45, 50, 50 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 FORMULA a(n) = card( k : sigma(k) < n ); a(n) is asymptotic to c*n with c=0.67... MAPLE N:= 100: # to get a(1)..a(N) V:= Vector(N): for n from 1 to N-2 do   s:= numtheory:-sigma(n)+1;   if s <= N then V[s]:= V[s]+1 fi; od: ListTools:-PartialSums(V); # Robert Israel, Jan 08 2018 PROG (PARI) a(n)=sum(i=1, n, if(1+sign(sigma(i)-n), 0, 1)) CROSSREFS Partial sums of A054973. Cf. A000203. Sequence in context: A320033 A064047 A111899 * A013928 A172104 A006161 Adjacent sequences:  A074750 A074751 A074752 * A074754 A074755 A074756 KEYWORD nonn AUTHOR Benoit Cloitre, Sep 28 2002 STATUS approved

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Last modified November 12 12:43 EST 2018. Contains 317109 sequences. (Running on oeis4.)