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 A356953 #67 Aug 31 2025 13:10:09 %S A356953 1,2,33,1083,602,2522,211673,6612470,3405122,49799889,202536181, %T A356953 3195380868,5208143601,85843948321,97524222465,361385490681003, %U A356953 441826936079342 %N A356953 Least nonzero starting number in the first run of exactly n consecutive numbers having the same number of prime factors counted with multiplicity, or -1 if no such number exists. %C A356953 In the definition, "exactly" means the run is not part of a longer run. %C A356953 a(18) > 2 * 10^15. - _Toshitaka Suzuki_, Aug 31 2025 %e A356953 2 and 3 are 2 consecutive numbers and have the same number of prime factors, and 2 is the smallest such number, hence a(2) = 2. %o A356953 (PARI) card(m)=my(c=0,k=bigomega(m));if(bigomega(m-1)!=k,while(bigomega(m)==k,c++;m++));c %o A356953 a(n)=if(n==1,return(1));for(m=2,+oo,if(card(m)==n,return(m))) %Y A356953 Cf. A001222, A077657, A356855. %Y A356953 Cf. A045920, A115186, A113752, A356893. %K A356953 nonn,more,changed %O A356953 1,2 %A A356953 _Jean-Marc Rebert_, Sep 06 2022 %E A356953 a(16)-a(17) from _Toshitaka Suzuki_, Aug 31 2025