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 A354984 #7 Jun 15 2022 14:36:49 %S A354984 12,21,39,48,57,75,93,111,129,147,183,192,201,219,237,291,309,327,363, %T A354984 381,417,453,471,489,507,543,579,597,633,669,687,723,768,813,831,849, %U A354984 867,921,939,993,1011,1029,1047,1083,1101,1119,1137,1191,1227,1263,1299,1317,1371,1389,1461,1497,1569,1587,1623,1641,1713 %N A354984 Numbers that are 3 * prime powers congruent to 1 (mod 3). %C A354984 Numbers k of the form 9m+3 such that k/3 = p^k, with p a prime and k >= 1. %F A354984 a(n) = 3 * A137827(n). %t A354984 Select[Range[2000], Mod[#, 9] == 3 && PrimePowerQ[#/3] &] (* _Amiram Eldar_, Jun 15 2022 *) %o A354984 (PARI) %o A354984 A354983(n) = ((3==(n%9)) && isprimepower(n/3)); %o A354984 isA354984(n) = A354983(n); %Y A354984 Intersection of A017197 and 3*A246655. %Y A354984 Cf. A137827, A354983 (characteristic function). %Y A354984 Row 3 of A354930 (conjectured). %K A354984 nonn %O A354984 1,1 %A A354984 _Antti Karttunen_, Jun 15 2022