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 A344978 #9 Jun 05 2021 16:44:16
%S A344978 21,26,39,50,57,74,75,78,93,98,111,122,129,146,147,150,183,194,201,
%T A344978 205,218,219,222,237,242,291,294,301,305,309,314,327,338,362,363,366,
%U A344978 381,386,405,417,438,452,453,458,471,482,489,505,507,543,554,578,579,582,597,605,610,626,633,654,657,669,674,676,687
%N A344978 Numbers k such that A011772(k) is equal to A344878(k), but k is not a power of prime.
%C A344978 Numbers k for which A344976(k) = 0, and A001221(k) > 1.
%F A344978 For all n, A344970(a(n)) = 1.
%o A344978 (PARI)
%o A344978 A011772(n) = { if(n==1, return(1)); my(f=factor(if(n%2, n, 2*n)), step=vecmax(vector(#f~, i, f[i, 1]^f[i, 2]))); forstep(m=step, 2*n, step, if(m*(m-1)/2%n==0, return(m-1)); if(m*(m+1)/2%n==0, return(m))); }; \\ From A011772
%o A344978 A344878(n) = if(1==n,n, my(f=factor(n)~); lcm(vector(#f, i, (f[1, i]^(f[2, i]+(2==f[1, i]))-1))));
%o A344978 isA344978(n) = (omega(n)>1&&(A344878(n)==A011772(n)));
%Y A344978 Cf. A000961, A001221, A011772, A344878, A344970, A344976.
%Y A344978 Subsequence of A344975. Intersection of A024619 and A344979.
%K A344978 nonn
%O A344978 1,1
%A A344978 _Antti Karttunen_, Jun 04 2021