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 A380478 #19 Feb 03 2025 17:03:06 %S A380478 1,6,14,26,38,62,74,86,122,134,146,158,186,194,206,218,254,278,302, %T A380478 314,326,362,386,398,422,434,446,458,482,542,554,566,614,626,662,674, %U A380478 698,734,746,758,794,818,842,854,866,878,906,914,926,974,998,1046,1082,1094,1142,1154,1202,1214,1226,1238,1262,1266,1286 %N A380478 Nonprime numbers k such that A380459(k) has no divisors of form p^p. %C A380478 See A380468 to find why each term must be squarefree. %C A380478 After the initial 1 all terms here are even (thus in A039956) because as A276086(k) flips the parity of k, having more than one odd prime factor in k without a single 2 would make A380459(k) a multiple of 4, and thus outside of A048103. %C A380478 For a similar reason, any term that is not a multiple of 3 may have at most 3 prime factors. %H A380478 Antti Karttunen, <a href="/A380478/b380478.txt">Table of n, a(n) for n = 1..20000</a> %H A380478 <a href="/index/Pri#primorialbase">Index entries for sequences related to primorial base</a>. %o A380478 (PARI) is_A380478 = A380477; %Y A380478 Cf. A048103, A276086, A380459, A380474 (subsequence), A380477 (characteristic function). %Y A380478 Intersection of A380468 and A018252. (A380468 without primes). %Y A380478 Subsequence of A000469. Subsequence of A039956 (after the initial 1). %K A380478 nonn %O A380478 1,2 %A A380478 _Antti Karttunen_, Feb 03 2025