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 A377462 #26 Nov 06 2024 04:39:03 %S A377462 1,3,0,7,0,12,0,15,3,0,0,28,0,0,8,31,0,39,0,42,0,0,0,60,5,0,0,56,0,72, %T A377462 0,63,0,0,12,91,0,0,0,90,0,96,0,0,32,0,0,124,7,15,0,0,0,120,0,120,0,0, %U A377462 0,168,0,0,16,127,0,144,0,0,0,36,0,195,0,0,0,0,18,0,0,186,9,0,0,224,0 %N A377462 a(n) is the size of the central part of the symmetric representation of sigma(n), or 0 if such a part does not exits. %C A377462 a(n) = A000203(n) if and only if n is a member of A174973. %e A377462 For n = 9 the symmetric representation of sigma(9) = 13 in the first quadrant looks like this: %e A377462 y %e A377462 . %e A377462 ._ _ _ _ _ 5 %e A377462 |_ _ _ _ _| %e A377462 . |_ _ 3 %e A377462 . |_ | %e A377462 . |_|_ _ 5 %e A377462 . | | %e A377462 . | | %e A377462 . | | %e A377462 . | | %e A377462 . . . . . . . . |_| . . x %e A377462 . %e A377462 There are three parts [5, 3, 5] and the central part is 3 so a(9) = 3. %Y A377462 Indices of odd terms give A028982. %Y A377462 Indices of even terms give A028983. %Y A377462 Indices of zeros give A071561. %Y A377462 Indices of nonzero terms give A071562. %Y A377462 Nonzero terms give A295423. %Y A377462 Parity gives A053866. %Y A377462 Has the same parity as A000203, A000593, A001227, A033879, A033880, A067742. %Y A377462 Cf. A174973, A196020, A235791, A236104, A237270, A237271, A237591, A237593, A241558, A241559, A245092, A262626, A347950. %K A377462 nonn %O A377462 1,2 %A A377462 _Omar E. Pol_, Oct 29 2024