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 A355177 #9 Jul 01 2022 20:09:23 %S A355177 2,3,6,10,12,15,18,24,26,28,33,48,63,66,70,72,78,80,82,84,90,105,108, %T A355177 110,114,120,130,132,140,156,165,170,174,182,190,192,195,222,234,238, %U A355177 242,252,258,264,273,276,280,290,294,306,308,310,315,318,336,342,345,350,354,357,366,372,374,378,380,385,396,399 %N A355177 Numbers k such that omega(k^2 - 1) = omega(k) where omega(k) = A001221(k). %F A355177 A001221(a(n)) = A082863(a(n)). %e A355177 10 is in the sequence because A001221(10^2 - 1) = A001221(3*3*11) = 2 and A001221(10) = A001221(2*5) = 2. %t A355177 Select[Range[400], PrimeNu[#] == PrimeNu[#^2 - 1] &] (* _Amiram Eldar_, Jun 22 2022 *) %o A355177 (Magma) [n: n in [2..400] | #PrimeDivisors(n^2-1) eq #PrimeDivisors(n)]; %o A355177 (PARI) is(n)=omega(n)==omega(n-1)+omega(n+1)-(n%2) \\ _Charles R Greathouse IV_, Jul 01 2022 %Y A355177 Cf. A001221, A082863, A190789. %K A355177 nonn,easy %O A355177 1,1 %A A355177 _Juri-Stepan Gerasimov_, Jun 22 2022