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A176504 a(n) = m + k where prime(m)*prime(k) = semiprime(n). 2
2, 3, 4, 4, 5, 5, 6, 6, 6, 7, 7, 8, 7, 9, 8, 10, 8, 9, 8, 10, 11, 12, 9, 11, 13, 9, 14, 10, 15, 12, 10, 13, 16, 11, 17, 14, 12, 18, 11, 10, 19, 15, 16, 12, 20, 17, 21, 11, 13, 22, 14, 23, 18, 13, 24, 12, 19, 25, 20, 15, 12, 26, 21, 27, 14, 16, 28, 13, 22, 29, 17, 15, 30, 23, 13, 31 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..76.

MAPLE

From R. J. Mathar, Apr 20 2010: (Start)

isA001358 := proc(n) numtheory[bigomega](n) = 2 ; end proc:

A001358 := proc(n) option remember ; if n = 1 then return 4 ; else for a from procname(n-1)+1 do if isA001358(a) then return a; end if; end do; end if; end proc:

A084126 := proc(n) min(op(numtheory[factorset](A001358(n)))) ; end proc:

A084127 := proc(n) max(op(numtheory[factorset](A001358(n)))) ; end proc:

A176504 := proc(n) numtheory[pi](A084126(n)) + numtheory[pi](A084127(n)) ; end proc: seq(A176504(n), n=1..80) ; (End)

CROSSREFS

Sequence in context: A027434 A319434 A174697 * A196162 A071940 A085883

Adjacent sequences:  A176501 A176502 A176503 * A176505 A176506 A176507

KEYWORD

nonn,changed

AUTHOR

Juri-Stepan Gerasimov, Apr 19 2010

EXTENSIONS

Entries checked by R. J. Mathar, Apr 20 2010

STATUS

approved

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Last modified February 17 10:59 EST 2019. Contains 320219 sequences. (Running on oeis4.)