cp's OEIS Frontend

A130208 Diagonalized matrix of A000203, sigma(n).

%I A130208 #11 Jan 17 2025 16:30:20
%S A130208 1,0,3,0,0,4,0,0,0,7,0,0,0,0,6,0,0,0,0,0,12,0,0,0,0,0,0,8,0,0,0,0,0,0,
%T A130208 0,15,0,0,0,0,0,0,0,0,13,0,0,0,0,0,0,0,0,0,18,0,0,0,0,0,0,0,0,0,0,12,
%U A130208 0,0,0,0,0,0,0,0,0,0,0,28,0,0,0,0,0,0,0,0,0,0,0,0,14,0,0,0,0,0,0,0,0,0,0,0,0,0,24,0,0,0,0,0,0,0,0,0,0,0,0,0,0,24
%N A130208 Diagonalized matrix of A000203, sigma(n).
%C A130208 A130207 replaces sigma(n) with phi(n), A000010. A130209 replaces sigma(n) with d(n), A000005.
%H A130208 Antti Karttunen, <a href="/A130208/b130208.txt">Table of n, a(n) for n = 1..22155; the first 210 rows of the triangle</a>
%F A130208 Infinite lower triangular matrix with A000203, sigma(n), in the main diagonal and the rest zeros.
%e A130208 First few rows of the triangle are:
%e A130208 1;
%e A130208 0, 3;
%e A130208 0, 0, 4;
%e A130208 0, 0, 0, 7;
%e A130208 0, 0, 0, 0, 6;
%e A130208 0, 0, 0, 0, 0, 12;
%e A130208 ...
%o A130208 (PARI) for(n=1,9,for(k=2,n,print1("0, "));print1(sigma(n)", ")) \\ _Charles R Greathouse IV_, Feb 14 2013
%o A130208 (PARI) A130208(n) = if(ispolygonal(n,3), sigma((sqrtint(1+(n*8))-1)/2), 0); \\ _Antti Karttunen_, Jan 17 2025
%Y A130208 Cf. A000203, A130207, A130209.
%K A130208 nonn,tabl
%O A130208 1,3
%A A130208 _Gary W. Adamson_, May 16 2007
%E A130208 Data section extended up to a(120) by _Antti Karttunen_, Jan 17 2025