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 A328456 #6 Oct 18 2019 16:46:02
%S A328456 0,1,2,3,1,4,5,2,6,7,3,8,2,1,9,10,4,6,11,5,12,13,2,14,3,6,15,4,7,16,
%T A328456 17,3,10,18,8,19,20,2,12,21,1,22,6,9,23,15,10,14,24,4,25,26,6,27,28,
%U A328456 11,29,8,5,6,4,12,2,30,13,31,21,2,32,33,14,20,18,3,34
%N A328456 LCM of the prime indices of 2n + 1, all minus 1; a(0) = 0.
%C A328456 A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
%e A328456 The prime indices of 2 * 17 + 1 = 35, all minus 1, are {2,3}, with LCM 6, so a(17) = 6.
%t A328456 Table[If[n==1,0,LCM@@(PrimePi/@First/@FactorInteger[n]-1)],{n,1,100,2}]
%Y A328456 Positions of records (first appearances) are A006005.
%Y A328456 The GCD of the prime indices of n, all minus 1, is A328167(n).
%Y A328456 The LCM of the prime indices of n, all plus 1, is A328219(n).
%Y A328456 Partitions whose parts minus 1 are relatively prime are A328170.
%Y A328456 Numbers whose prime indices minus 1 are relatively prime are A328168.
%Y A328456 Cf. A056239, A112798, A258409, A289508, A289509, A290103, A318981, A328169, A328451.
%K A328456 nonn
%O A328456 0,3
%A A328456 _Gus Wiseman_, Oct 17 2019