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A144586 a(n) = odd and nonprime sum of prime factors of composite(k) = A002808(k). 0
9, 9, 9, 15, 9, 21, 15, 25, 33, 21, 39, 45, 27, 49, 15, 55, 15, 33, 63, 35, 15, 15, 69, 75, 15, 25, 81, 15, 45, 85, 25, 91, 15, 51, 15, 99, 21, 105, 21, 57, 15, 111, 115, 21, 35, 21, 63, 15, 65, 129, 25, 35, 133, 25, 21, 141, 75, 27, 77, 153, 27, 25, 159, 165, 21, 87, 169, 27 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..68.

EXAMPLE

At k=7, A002808(k) = 14 = 2*7, and 2 + 7 = 9 (an odd nonprime), and k=7 is the smallest index for which this occurs, so a(1)=9.

At k=11, A002808(k) = 20 = 2*2*5, and 2 + 2 + 5 = 9 (an odd nonprime), and k=11 is the 2nd smallest index for which this occurs, so a(2)=9.

At k=14, A002808(k) = 24 = 2*2*2*3, and 2 + 2 + 2 + 3 = 9 (an odd nonprime), and k=24 is the 3rd smallest index for which this occurs, so a(3)=9.

At k=16, A002808(k) = 26 = 2*13 and 2 + 13 = 15 (an odd nonprime), and k=26 is the 4th smallest index for which this occurs, so a(4)=15, etc.

MAPLE

# R. J. Mathar, May 01 2010: (Start)

pss := proc(n) a := 0 ; for d in ifactors(n)[2] do a := a+ op(2, d)*op(1, d) ; end do: a ; end proc:

A002808 := proc(n) if n = 1 then 4; else for a from procname(n-1)+1 do if not isprime(a) then return a; end if; end do: end if; end proc:

A046343 := proc(n) pss(A002808(n)) ; end proc:

for k from 1 to 800 do a := A046343(k) ; if not isprime(a) and type(a, 'odd') then printf("%d, ", a) ; end if; end do: # (End)

CROSSREFS

Cf. A002808, A141468.

Sequence in context: A068395 A245429 A242893 * A141557 A072563 A206011

Adjacent sequences:  A144583 A144584 A144585 * A144587 A144588 A144589

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Jan 04 2009

EXTENSIONS

Corrected at two or more places and extended by R. J. Mathar, May 01 2010

Example section edited by Jon E. Schoenfield, Oct 18 2015

STATUS

approved

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Last modified July 1 16:11 EDT 2016. Contains 274321 sequences.