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A090076 a(n) = prime(n)*prime(n+2).

%I A090076 #32 Sep 24 2023 07:51:35
%S A090076 10,21,55,91,187,247,391,551,713,1073,1271,1591,1927,2279,2773,3233,
%T A090076 3953,4331,4891,5609,6059,7031,8051,8989,9991,10807,11227,12091,13843,
%U A090076 14803,17399,18209,20413,20989,23393,24613,26219,28199,29893,31313
%N A090076 a(n) = prime(n)*prime(n+2).
%C A090076 Subsequence of A192133. - _Reinhard Zumkeller_, Jun 26 2011
%C A090076 For n > 1: A078898(a(n)) = 4. - _Reinhard Zumkeller_, Apr 06 2015
%H A090076 Reinhard Zumkeller, <a href="/A090076/b090076.txt">Table of n, a(n) for n = 1..10000</a>
%H A090076 C. Cobeli and A. Zaharescu, <a href="http://dx.doi.org/10.1080/10236198.2014.940337">A game with divisors and absolute differences of exponents</a>, Journal of Difference Equations and Applications, Vol. 20, #11 (2014) pp. 1489-1501, DOI: 10.1080/10236198.2014.940337. Also available as <a href="http://arxiv.org/abs/1411.1334">arXiv:1411.1334 [math.NT]</a>, 2014.
%e A090076 a(5) = prime(5)*prime(7) = 11*17 = 187.
%t A090076 Table[Prime[n] Prime[n + 2], {n, 1, 40}] (* _Robert G. Wilson v_, Jan 22 2004 *)
%t A090076 Last[#]First[#]&/@Partition[Prime[Range[50]],3,1] (* _Harvey P. Dale_, May 08 2013 *)
%o A090076 (MuPAD) ithprime(i)*ithprime(i+2) $ i = 1..40 // _Zerinvary Lajos_, Feb 26 2007
%o A090076 (Sage)
%o A090076 def prime_gaps(n):
%o A090076     primegaps = []
%o A090076     nprimes = primes_first_n(n+1)
%o A090076     for i in range(2, n+1):
%o A090076         primegaps.append(nprimes[i]*nprimes[i-2])
%o A090076     return primegaps
%o A090076 print(prime_gaps(60)) # _Zerinvary Lajos_, Jul 08 2008
%o A090076 (Haskell)
%o A090076 a090076 n = a090076_list !! (n-1)
%o A090076 a090076_list = zipWith (*) a000040_list $ drop 2 a000040_list
%o A090076 -- _Reinhard Zumkeller_, Dec 17 2014
%Y A090076 Subset of the squarefree semiprimes, A006881. Cf. A006094, A090090.
%Y A090076 Cf. A078898.
%K A090076 easy,nonn
%O A090076 1,1
%A A090076 _Felix Tubiana_, Jan 21 2004
%E A090076 Extended by _Robert G. Wilson v_, Jan 22 2004