

A206011


The nth semiprime minus its sum of digits.


1



0, 0, 0, 9, 9, 9, 18, 18, 18, 18, 27, 27, 27, 27, 27, 36, 36, 45, 45, 45, 45, 54, 54, 54, 63, 63, 72, 72, 72, 72, 81, 81, 81, 81, 99, 108, 108, 108, 108, 117, 117, 117, 117, 126, 126, 135, 135, 135, 135, 135, 144, 144, 144, 153, 153, 153, 162, 162, 171, 171
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OFFSET

1,4


COMMENTS

This is to semiprimes A001358 as A068395 is to primes A000040. As with A068395, this is always a multiple of 9, hence cannot be prime. But, as happens first for a(4), a(n) can be semiprime.


LINKS

Table of n, a(n) for n=1..60.


FORMULA

a(n) = A001358(n)  A007953(A001358(n)).


EXAMPLE

a(4) = 10  1 = 9.
a(5) = 14  5 = 9.


MAPLE

read("transforms") :
A206011 := proc(n)
s := A001358(n) ;
s digsum(s) ;
end proc: # R. J. Mathar, Sep 14 2012


CROSSREFS

Cf. A000040, A001358, A007953, A068395.
Sequence in context: A144586 A141557 A072563 * A192984 A069602 A160761
Adjacent sequences: A206008 A206009 A206010 * A206012 A206013 A206014


KEYWORD

nonn,easy,base


AUTHOR

Jonathan Vos Post, Feb 02 2012


STATUS

approved



