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Numbers k such that k and k+1 have the same sum of non-unitary divisors (A048146), for A048146(k) > 0.
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%I #24 Jun 11 2019 00:10:20

%S 188,1484,3915,14750,19196,20150,79947,164996,190484,219375,253827,

%T 639387,718011,835515,1172374,1380483,2026323,2064249,3611708,5507540,

%U 6128108,6374403,6872984,10073132,10558250,11360547,12770450,13000635,14458364,16366292,19127907

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

%C The sequence snud(a(n)) = snud(1 + a(n)) is A103846(n). - _Emeric Deutsch_, Feb 17 2005

%H Giovanni Resta, <a href="/A064115/b064115.txt">Table of n, a(n) for n = 1..344</a> (terms < 10^11, first 30 terms from Harry J. Smith)

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

%t 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 *)

%o (PARI) snud(n)= { sumdiv(n, d, if(gcd(d, n/d)!=1, d)) }

%o { 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

%Y Cf. A048146, A103846.

%K nonn

%O 1,1

%A _Jason Earls_, Sep 09 2001

%E More terms from _Emeric Deutsch_, Feb 17 2005