OFFSET
1,1
COMMENTS
Elements in this sequence can themselves be 4-almost primes. a(1) = 16 = 2^4. a(2) = 40 = 2^3 * 5. a(19) = 1652 = 2^2 * 7 * 59. a(20) = 1804 = 2^2 * 11 * 41. a(31) = 4046 = 2 * 7 * 17^2. a(37) = 5608 = 2^3 * 701. a(39) = 6201 = 3^2 * 13 * 53. a(40) = 6507 = 3^3 * 241. a(42) = 7130 = 2 * 5 * 23 * 31. a(43) = 7458 = 2 * 3 * 11 * 113. Does this happen infinitely often? - Jonathan Vos Post, Dec 11 2004
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
FORMULA
a(n) = sum_{i=1..n} A014613(i). - R. J. Mathar, Sep 14 2012
EXAMPLE
a(2)=40 because sum of first two 4-almost primes i.e. 16+24 is 40.
MATHEMATICA
Accumulate[Select[Range[1000], PrimeOmega[#]==4&]] (* Harvey P. Dale, Feb 07 2014 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Shyam Sunder Gupta, Aug 24 2003
STATUS
approved