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 A274333 #27 May 07 2025 12:35:49 %S A274333 0,2,4,5,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,24,26,27,28,30,31, %T A274333 33,36,37,38,41,47,49,53,54,56,61,62,66,68,70,71,72,76,78,79,80,86,90, %U A274333 91,96,110,113,117,120,121,136,140,144,164,168,172,178,202,203 %N A274333 Indices of Lucas numbers having exactly one primitive prime factor. %C A274333 0 together with numbers n such that A086600(n) = 1, except if n = 3. %C A274333 The only primes in this sequence are the prime numbers in A001606, which gives the indices of prime Lucas numbers. %H A274333 Arkadiusz Wesolowski, <a href="/A274333/b274333.txt">Table of n, a(n) for n = 1..102</a> %o A274333 (Magma) lst:=[]; pr:=1; for n in [0..203] do pd:=PrimeDivisors(Lucas(n)); d:=1; t:=0; for c in [1..#pd] do f:=pd[c]; if Gcd(pr, f) eq 1 then t+:=1; else d:=d*f; end if; end for; if t eq 1 then Append(~lst, n); end if; pr:=pr*Truncate(Lucas(n)/d); end for; lst; %Y A274333 Cf. A000032, A001606, A058036, A086600. %K A274333 nonn %O A274333 1,2 %A A274333 _Arkadiusz Wesolowski_, Jun 22 2016