A286837 Numbers n such that usigma(n) = usigma(2*n+1) where usigma(n) = A034448(n).

1386, 6790, 8130, 18618, 21378, 27654, 38874, 60030, 64020, 71058, 89178, 92130, 97014, 117114, 118902, 180438, 182226, 224058, 247044, 396078, 495114, 510906, 528510, 723486, 855966, 979098, 1007562, 1012380, 1032360, 1141194, 1302906, 1410294

Offset

1,1

Comments

46495995 = 3*5*7*13*23*1481 is the smallest odd term of this sequence.

Links

Amiram Eldar, Table of n, a(n) for n = 1..1000

Mathematica

usigma[1] = 1;  usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); Select[Range[10^5], usigma[#] == usigma[2#+1] &] (* Amiram Eldar, Aug 04 2019 *)

Prog

(PARI) a034448(n) = sumdivmult(n, d, if(gcd(d, n/d)==1, d));
isok(n) = a034448(n)==a034448(2*n+1); \\ after Charles R Greathouse IV at A034448

Crossrefs

Cf. A034448, A064125, A272553.

Sequence in context: A212222 A045103 A175695 * A023090 A236823 A092721

Adjacent sequences: A286834 A286835 A286836 * A286838 A286839 A286840

Keyword

nonn

Author

Altug Alkan, Aug 01 2017

Status

approved