A204823 Sum of divisors (A000203) of deficient numbers (A005100).

1, 3, 4, 7, 6, 8, 15, 13, 18, 12, 14, 24, 24, 31, 18, 20, 32, 36, 24, 31, 42, 40, 30, 32, 63, 48, 54, 48, 38, 60, 56, 42, 44, 84, 78, 72, 48, 57, 93, 72, 98, 54, 72, 80, 90, 60, 62, 96, 104, 127, 84, 68, 126, 96, 72, 74, 114, 124, 140, 96, 80, 121, 126, 84, 108, 132

Offset: 1

Author

Jaroslav Krizek, Jan 22 2012

Keywords

• nonn

Comments

a(n) = A000203(A005100(n)) = A005100(n) + A205099(n).

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000
• Eric Weisstein's World of Mathematics, Deficient Number

Crossrefs

Cf. A204822 (sum of divisors of abundant numbers), A205099 (sum of proper divisors of deficient numbers).

Programs

Mathematica

sddn[n_]:=Module[{s=DivisorSigma[1,n]},If[s<2n,s,0]]; DeleteCases[ sddn/@ Range[ 100],0] (* Harvey P. Dale, Jan 02 2015 *)

PARI

for(n=1,300,s=sigma(n);if(s<2*n,print1(s", "))) \\ Charles R Greathouse IV, Feb 19 2013

Formula

a(n) < 8n/3. - Charles R Greathouse IV, Feb 19 2013