This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A190789 #18 Jul 31 2017 12:43:11 %S A190789 2,6,10,12,18,24,26,28,48,66,70,72,78,80,82,84,90,108,110,114,120,130, %T A190789 132,140,156,170,174,182,190,192,222,234,238,242,252,255,258,264,276, %U A190789 280,290,294,306,308,310,318,336,342,350,354,366,372,374,378,380,396,402,408,410,418 %N A190789 Numbers n such that omega(n-1) + omega(n+1) = omega(n) where omega(n) = A001221(n). %H A190789 Charles R Greathouse IV, <a href="/A190789/b190789.txt">Table of n, a(n) for n = 1..10000</a> %F A190789 omega(a(n)-1) + omega(a(n)+1) = omega(a(n)). %e A190789 a(35)=255 because omega(254)+omega(256)=omega(255) or 2+1=3. %t A190789 Select[Range[5000], PrimeNu[# - 1] + PrimeNu[# + 1] == PrimeNu[ #] &] (* _G. C. Greubel_, Apr 24 2017 *) %t A190789 Flatten[Position[Partition[PrimeNu[Range[450]],3,1],_?(#[[1]]+#[[3]] == #[[2]]&),1,Heads->False]]+1 (* _Harvey P. Dale_, Jul 31 2017 *) %o A190789 (PARI) isok(n) = omega(n) == omega(n-1) + omega(n+1); \\ _Michel Marcus_, Apr 25 2017 %Y A190789 Cf. A001221. %K A190789 nonn,easy %O A190789 1,1 %A A190789 _Juri-Stepan Gerasimov_, May 19 2011 %E A190789 a(18) corrected, a(22) added by _Charles R Greathouse IV_, May 24 2011