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A086046 Sum of first n 4-almost primes. 6
16, 40, 76, 116, 170, 226, 286, 367, 451, 539, 629, 729, 833, 959, 1091, 1226, 1362, 1502, 1652, 1804, 1960, 2144, 2333, 2529, 2727, 2931, 3141, 3361, 3586, 3814, 4046, 4280, 4528, 4778, 5038, 5314, 5608, 5904, 6201, 6507, 6815, 7130, 7458, 7788, 8128 (list; graph; refs; listen; history; text; internal format)
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

Sequence in context: A177723 A174321 A258258 * A184030 A182461 A205065

Adjacent sequences:  A086043 A086044 A086045 * A086047 A086048 A086049

KEYWORD

easy,nonn

AUTHOR

Shyam Sunder Gupta, Aug 24 2003

STATUS

approved

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Last modified September 26 11:09 EDT 2021. Contains 347665 sequences. (Running on oeis4.)