A064115 Numbers k such that k and k+1 have the same sum of non-unitary divisors (A048146), for A048146(k) > 0.

188, 1484, 3915, 14750, 19196, 20150, 79947, 164996, 190484, 219375, 253827, 639387, 718011, 835515, 1172374, 1380483, 2026323, 2064249, 3611708, 5507540, 6128108, 6374403, 6872984, 10073132, 10558250, 11360547, 12770450, 13000635, 14458364, 16366292, 19127907

Offset

1,1

Comments

The sequence snud(a(n)) = snud(1 + a(n)) is A103846(n). - Emeric Deutsch, Feb 17 2005

Links

Giovanni Resta, Table of n, a(n) for n = 1..344 (terms < 10^11, first 30 terms from Harry J. Smith)

Example

snud(1484) = 864, snud(1485) = 864.

Mathematica

nusigma[1]=0; nusigma[n_] := DivisorSigma[1, n] - Times @@ (1 + Power @@@ FactorInteger[n]); seq={}; s1=0; Do[s2=nusigma[n]; If[s1>0 && s2==s1, AppendTo[seq, n-1]]; s1=s2, {n, 1, 10^6}]; seq (* Amiram Eldar, Jun 10 2019 *)

Prog

(PARI) snud(n)= { sumdiv(n, d, if(gcd(d, n/d)!=1, d)) }
{ n=0; for (m=1, 10^9, s=snud(m); if (s>0 && s==snud(m + 1), write("b064115.txt", n++, " ", m); if (n==30, break)) ) } \\ Harry J. Smith, Sep 07 2009

Crossrefs

Cf. A048146, A103846.

Sequence in context: A233786 A233961 A073586 * A185241 A211818 A204071

Adjacent sequences: A064112 A064113 A064114 * A064116 A064117 A064118

Keyword

nonn

Author

Jason Earls, Sep 09 2001

Extensions

More terms from Emeric Deutsch, Feb 17 2005

Status

approved