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A086062 Sum of first n 3-almost primes. 6
8, 20, 38, 58, 85, 113, 143, 185, 229, 274, 324, 376, 439, 505, 573, 643, 718, 794, 872, 964, 1062, 1161, 1263, 1368, 1478, 1592, 1708, 1825, 1949, 2074, 2204, 2342, 2489, 2637, 2790, 2944, 3108, 3273, 3443, 3614, 3786, 3960, 4135, 4317, 4503, 4691, 4881 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Elements in this sequence can themselves be 3-almost primes. a(1) = 8 = 2^3. a(2) = 20 = 2^2 * 5. a(20) = 964 = 2^2 * 241. a(28) = 1825 = 5^2 * 73. a(30) = 2074 = 2 * 17 * 61. a(34) = 2637 = 3^2 * 293. a(40) = 3614 = 2 * 13 * 139. a(41) = 3786 = 2 * 3 * 631. a(45) = 4503 = 3 * 19 * 79. Does this happen infinitely often? - Jonathan Vos Post, Dec 11 2004

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = sum_{i=1..n} A014612(i). - R. J. Mathar, Sep 14 2012

EXAMPLE

a(2)=20 because sum of first two 3-almost primes i.e. 8+12 is 20.

MATHEMATICA

Accumulate[Select[Range[500], PrimeOmega[#]==3&]] (* Harvey P. Dale, Jan 17 2014 *)

CROSSREFS

Sequence in context: A272805 A073607 A351967 * A006416 A273069 A273144

Adjacent sequences: A086059 A086060 A086061 * A086063 A086064 A086065

KEYWORD

easy,nonn

AUTHOR

Shyam Sunder Gupta, Aug 24 2003

STATUS

approved

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Last modified January 27 06:42 EST 2023. Contains 359837 sequences. (Running on oeis4.)