A159953 Values in A054973 larger than 1.

2, 2, 3, 2, 2, 3, 3, 2, 2, 3, 5, 2, 3, 3, 4, 2, 2, 2, 2, 4, 2, 2, 2, 2, 2, 5, 2, 2, 6, 4, 2, 2, 5, 2, 5, 3, 3, 3, 7, 3, 6, 2, 3, 2, 2, 6, 3, 2, 4, 2, 3, 8, 2, 9, 4, 2, 6, 2, 2, 2, 2, 2, 2, 4, 8, 4, 2, 2, 2, 3, 4, 3, 9, 2, 10, 2, 3, 2, 4, 4, 3, 4, 2, 2, 11, 5, 2, 5, 2, 3, 4, 2, 2, 3, 5, 3, 8, 7, 4, 15, 2, 4, 7, 8

Offset

1,1

Comments

This is a survey of how many solutions the equation sigma(x)=k has for k in A159886, or about the lengths of the plateaus in A007609.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1095 from Jean-François Alcover)

Max Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems (invphi.gp).

Maple

read("transforms3") ; a054973 := BFILETOLIST("b054973.txt") ;
for i from 1 to 1000 do if op(i, a054973) > 1 then printf("%d, ", op(i, a054973)) ; fi; od: # R. J. Mathar, May 22 2009

Mathematica

b[n_] := Sum[Boole[DivisorSigma[1, k] == n], {k, 1, n}];
Select[Array[b, 1000], # > 1&] (* Jean-François Alcover, Apr 06 2020 *)

Prog

(PARI) list(lim) = {my(s); for(k = 1, lim, s = invsigmaNum(k); if(s > 1, print1(s, ", "))); } \\ Amiram Eldar, Dec 25 2024, using Max Alekseyev's invphi.gp

Crossrefs

Cf. A000203, A007609, A054973, A159886.

Sequence in context: A002233 A241516 A273458 * A074595 A372754 A084126

Adjacent sequences: A159950 A159951 A159952 * A159954 A159955 A159956

Keyword

nonn,changed

Author

Jaroslav Krizek, Apr 27 2009

Extensions

Edited and extended by R. J. Mathar, May 22 2009

Status

approved