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A131848 Least nonnegative number which when added to the n-th semiprime gives a multiple of n.

%I A131848 #9 Mar 23 2013 11:28:20
%S A131848 0,0,0,2,1,3,0,2,2,4,0,2,4,4,6,2,2,3,2,3,5,4,4,3,1,1,26,27,1,3,2,3,5,
%T A131848 7,34,33,33,34,37,39,1,3,0,43,1,43,46,1,2,4,49,50,0,1,54,55,51,54,53,
%U A131848 55,57,54,51,54,57,59,62,63,63,66,69,71,1,3,4,2,73,75,69,71
%N A131848 Least nonnegative number which when added to the n-th semiprime gives a multiple of n.
%C A131848 This is to semiprimes A001358 as A068901 is to primes A000040.
%H A131848 Harvey P. Dale, <a href="/A131848/b131848.txt">Table of n, a(n) for n = 1..1000</a>
%F A131848 a(n) = MIN{k=>0 such that n|(k+A001358(n))}.
%e A131848 a(1) = 0 because 1 | (0+semiprime(1)=4).
%e A131848 a(6) = 3 because 6 | (3+semiprime(3)=3+15=18).
%e A131848 a(25) = 1 because 25 | (1+semiprime(25)=1+74=75).
%t A131848 lnn[{s_,n_}]:=If[Divisible[s,n],0,n-Mod[s,n]]; lnn/@Module[{sp=Select[ Range[ 300], PrimeOmega[#] ==2&], len},len=Length[sp];Thread[{sp,Range[len]}]] (* _Harvey P. Dale_, Mar 23 2013 *)
%Y A131848 Cf. A000040, A001358, A068901.
%K A131848 easy,nonn
%O A131848 1,4
%A A131848 _Jonathan Vos Post_, Oct 04 2007
%E A131848 More terms from _R. J. Mathar_, Jan 15 2008