A083682 Sum of aliquot divisors of semiprimes.

3, 6, 4, 8, 10, 9, 11, 14, 6, 16, 15, 20, 13, 22, 17, 26, 8, 21, 17, 23, 32, 34, 19, 27, 40, 19, 44, 23, 46, 33, 21, 35, 50, 25, 56, 41, 29, 62, 25, 12, 64, 45, 47, 27, 70, 51, 74, 25, 35, 76, 37, 82, 57, 31, 86, 14, 63, 92, 65, 43, 29, 100, 71, 104, 37, 47, 106, 31, 75, 110, 49

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = A001065(A001358(n)). - Amiram Eldar, Sep 23 2019

Example

a(1)=3 because sum of aliquot divisors of first semiprime i.e. 4 is 1+2=3.

Mathematica

s[n_] := DivisorSigma[1, n] - n; s /@ Select[Range[300], PrimeOmega[#]==2 &] (* Amiram Eldar, Sep 23 2019 *)

Crossrefs

Cf. A001065, A001358.

Sequence in context: A154890 A248176 A100000 * A379531 A021278 A372789

Adjacent sequences: A083679 A083680 A083681 * A083683 A083684 A083685

Keyword

easy,nonn

Author

Shyam Sunder Gupta, Jun 15 2003

Status

approved