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 A121858 #17 Oct 08 2022 22:12:03 %S A121858 3,9,81,729,59049,531441,43046721,387420489,31381059609, %T A121858 22876792454961,205891132094649,150094635296999121, %U A121858 12157665459056928801,109418989131512359209,8862938119652501095929,6461081889226673298932241 %N A121858 Smallest odd number having prime(n) divisors, where prime(n) is the n-th prime=A000040(n). %C A121858 a(n) is also the smallest number k with the property that the symmetric representation of sigma(k) has prime(n) subparts. - _Omar E. Pol_, Oct 08 2022 %F A121858 a(n) = 3^(prime(n)-1) = 3^A006093(n). %F A121858 a(n) = A038547(A000040(n)). - _Omar E. Pol_, Oct 08 2022 %t A121858 3^(Prime[Range[20]]-1) (* _Harvey P. Dale_, Mar 19 2013 *) %Y A121858 Cf. A006093, A061286. %Y A121858 Cf. A000040, A038546, A237593, A279387. %K A121858 nonn %O A121858 1,1 %A A121858 _Lekraj Beedassy_, Aug 30 2006