A062832 Numbers k such that k and k+2 have the same number of divisors.

3, 5, 6, 8, 11, 17, 18, 29, 33, 40, 41, 50, 54, 55, 59, 71, 85, 91, 93, 101, 102, 107, 123, 128, 136, 137, 141, 143, 149, 152, 159, 179, 182, 183, 184, 185, 191, 197, 198, 201, 203, 213, 215, 217, 219, 227, 230, 235, 239, 242, 243, 246, 247, 248, 265, 269, 281

Offset

1,1

Comments

The lesser member of every twin-prime pair occurs in this sequence. Hence A001359 is a subsequence. - T. D. Noe, Sep 17 2007

Links

Giovanni Resta, Table of n, a(n) for n = 1..10000 (first 1000 terms from T. D. Noe)

Mathematica

Select[Range[300], DivisorSigma[0, #]==DivisorSigma[0, #+2]&] (* Harvey P. Dale, Mar 01 2012 *)
Position[Partition[DivisorSigma[0, Range[300]], 3, 1], _?(#[[1]]==#[[3]]&)]// Flatten//Quiet (* Harvey P. Dale, Mar 17 2017 *)

Prog

(PARI) je=[]; for(n=1, 1000, a=numdiv(n); b=numdiv(n+2); if(a==b, je=concat(je, n))); je

Crossrefs

Equals A067888 - 1. - Michel Marcus, Feb 11 2018

Sequence in context: A160734 A121501 A327218 * A089085 A033163 A228372

Adjacent sequences: A062829 A062830 A062831 * A062833 A062834 A062835

Keyword

nonn

Author

Jason Earls, Jul 20 2001

Status

approved