A168472 Partial sums of products of two distinct primes (A006881).

6, 16, 30, 45, 66, 88, 114, 147, 181, 216, 254, 293, 339, 390, 445, 502, 560, 622, 687, 756, 830, 907, 989, 1074, 1160, 1247, 1338, 1431, 1525, 1620, 1726, 1837, 1952, 2070, 2189, 2311, 2434, 2563, 2696, 2830, 2971, 3113, 3256, 3401, 3547, 3702, 3860, 4019

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Nov 26 2009

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Programs

Maple

N:= 1001: # to get all a(n) where A006881(n) < N
Primes:= select(isprime, [2, seq(2*k+1, k=1..floor(N/2))]):
L:= sort(convert({seq(seq(p*q, q=Primes[1..ListTools:-BinaryPlace(Primes, N/p)]), p=Primes)} minus {seq(p^2, p=Primes)},list)):
ListTools:-PartialSums(L); # Robert Israel, Apr 29 2018

Mathematica

f[n_]:=Last/@FactorInteger[n]=={1,1}; s=0;lst={};Do[If[f[n],AppendTo[lst,s+=n]],{n,6!}];lst
With[{nn=50},Take[Accumulate[Union[Times@@@Subsets[Prime[Range[nn]],{2}]]],nn]] (* Harvey P. Dale, Aug 08 2013 *)