A241838 Column 1 of A237270, also the right border.

1, 3, 2, 7, 3, 12, 4, 15, 5, 9, 6, 28, 7, 12, 8, 31, 9, 39, 10, 42, 11, 18, 12, 60, 13, 21, 14, 56, 15, 72, 16, 63, 17, 27, 18, 91, 19, 30, 20, 90, 21, 96, 22, 42, 23, 36, 24, 124, 25, 39, 26, 49, 27, 120, 28, 120, 29, 45, 30, 168, 31, 48, 32, 127

Offset: 1

Author

Omar E. Pol, Apr 29 2014

Keywords

• nonn
• look

Comments

First differs from A241559 at a(45).

If A237271(n) = 1 then a(n) = A241558(n) = A241559(n) = A000203(n).

If n is an odd prime then a(n) = (n + 1)/2 = A241558(n) = A241559(n).

For more information see A237593.

Examples

			For n = 45 the symmetric representation of sigma(45) = 78 has three parts [23, 32, 23], both the first and the last term are equal to 23, so a(45) = 23.
		

Links

• Robert Price, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000203, A071561, A071562, A196020, A235791, A236104, A237270, A237271, A237591, A237593, A239660, A239931-A239934, A241558, A241559, A245092, A262626.

Programs

Mathematica

Map[First[a237270[#]]&,Range[64]] (* data : computing all parts *)
(* computing only the first part of the symmetric representation of sigma(n) *)
row[n_] := Floor[(Sqrt[8n+1]-1)/2] (* in A237591 *)
f[n_, k_] := If[Mod[n-k*(k+1)/2, k]==0, (-1)^(k+1), 0]
g[n_, k_] := Ceiling[(n+1)/k-(k+1)/2] - Ceiling[(n+1)/(k+1)-(k+2)/2] (* in A237591 *)
a241838[n_] := Module[{r=row[n], widths={}, i=1, w=0, len, legs}, w+=f[n, i]; While[i<=r && w!=0, AppendTo[widths, w]; i++; w+=f[n, i]]; len=Length[widths]; legs=Map[g[n, #]&, Range[len]]; If[lenHartmut F. W. Hoft, Jan 25 2018 *)

Formula

a(n) = A237270(n, 1) = A237270(n, A237271(n)).