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%I #20 Jul 21 2021 11:56:00
%S 199,307,341,349,351,415,491,737,739,851,949,1013,1061,1149,1205,1211,
%T 1275,1277,1313,1315,1421,1667,1695,1747,1925,2049,2149,2276,2357,
%U 2365,2683,2717,2827,2889,2891,2949,3051,3115,3173,3259,3475,3581,3651,3797,4013,4045,4149,4193,4449,4597,4627,4654,4843
%N Numbers n such that d(n-1)=d(n+1)=12 where d(k)=A000005(k) (number of divisors of k).
%H G. C. Greubel, <a href="/A190355/b190355.txt">Table of n, a(n) for n = 1..5000</a>
%F A000005(a(n)-1) = A000005(a(n)+1) = 12.
%t Select[Range[2, 8000], DivisorSigma[0, # - 1] == 12 && DivisorSigma[0, # + 1] == 12 &] (* _G. C. Greubel_, Dec 29 2017 *)
%t SequencePosition[DivisorSigma[0,Range[5000]],{12,_,12}][[All,1]]+1 (* _Harvey P. Dale_, Jul 21 2021 *)
%o (PARI) for(n=2,10^4,if( numdiv(n-1)==12 && numdiv(n+1)==12, print1(n,", "))); /* _Joerg Arndt_, May 13 2011 */
%Y Cf. A189974, A190267.
%K nonn
%O 1,1
%A _Juri-Stepan Gerasimov_, May 09 2011
%E Terms corrected by _R. J. Mathar_, May 25 2011
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