A228378 Numbers n such that tb(n) = tb(n+1) where tb(n) = A048784(n) is the number of divisors of binomial(2*n, n).

9, 10, 22, 34, 44, 45, 51, 56, 82, 106, 130, 141, 142, 162, 166, 177, 185, 190, 230, 262, 273, 274, 320, 322, 346, 352, 354, 394, 440, 454, 470, 526, 536, 550, 562, 586, 606, 624, 635, 670, 692, 717, 754, 766, 779, 814, 826, 831, 862, 882, 891, 920, 934

Offset: 1

Author

Michel Marcus, Aug 21 2013

Keywords

• nonn

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..2611

Crossrefs

Cf. A000005, A000984.

Programs

Mathematica

SequencePosition[Table[DivisorSigma[0,Binomial[2n,n]],{n,1000}],{x_,x_}][[All,2]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Apr 15 2019 *)

PARI

lista(nn) = my(last = 0); for (i=1, nn, new = numdiv(binomial(2*i,i)); if (last == new, print1(i, ", ")); last = new) \\ Michel Marcus, Aug 21 2013