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A163506 a(n) = n-th odd nonprime * n-th odd number.

%I A163506 #14 May 05 2019 00:36:41
%S A163506 1,27,75,147,225,297,429,525,663,855,1029,1173,1375,1539,1827,2015,
%T A163506 2277,2625,2849,3159,3485,3741,4095,4371,4655,5049,5565,6105,6555,
%U A163506 6903,7259,7623,7995,8375,8901,9443,9855,10575,11011,11455,11907,12699,13175,13833
%N A163506 a(n) = n-th odd nonprime * n-th odd number.
%H A163506 G. C. Greubel, <a href="/A163506/b163506.txt">Table of n, a(n) for n = 1..1000</a>
%F A163506 a(n) = A014076(n)*A005408(n-1). - corrected by _R. J. Mathar_, Oct 10 2009
%e A163506 a(1) =  1*1 =   1;
%e A163506 a(2) =  9*3 =  27;
%e A163506 a(3) = 15*5 =  75;
%e A163506 a(4) = 21*7 = 147;
%e A163506 a(5) = 25*9 = 225.
%p A163506 A014076 := proc(n) option remember; local a; if n = 1 then 1; else for a from procname(n-1)+2 by 2 do if not isprime(a) then return a; end if; end do: end if; end proc:
%p A163506 A163506 := proc(n) A014076(n) *(2*n-1); end: seq(A163506(n),n=1..80) ; # _R. J. Mathar_, Oct 10 2009
%t A163506 A014076 := Select[Range[1, 10000, 2], PrimeOmega[#] != 1 &]; Table[A014076[[n]]*(2*n - 1), {n, 1, 50}] (* _G. C. Greubel_, Jul 27 2017 *)
%Y A163506 Cf. A005408, A014076.
%K A163506 nonn
%O A163506 1,2
%A A163506 _Juri-Stepan Gerasimov_, Jul 29 2009
%E A163506 7279 replaced with 7259 by _R. J. Mathar_, Oct 10 2009