Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #17 Jun 28 2018 02:49:07
%S 14,206,1334,1634,2685,14841,18873,19358,26872,33998,36566,42818,
%T 56564,84134,116937,122073,161001,162602,166934,174717,190773,193893,
%U 239499,245768,260096,289454,326884,383594,409695,422073,430137,438993,440013
%N Numbers k such that sigma(k)*omega(k) = sigma(k+1)*omega(k+1), where omega(k) is the number of distinct prime divisors of n (A001221).
%H Giovanni Resta, <a href="/A063071/b063071.txt">Table of n, a(n) for n = 1..1000</a> (first 100 terms from Harry J. Smith)
%t Select[Range[5000], PrimeNu[#]*DivisorSigma[1, #] == PrimeNu[# + 1]*DivisorSigma[1, # + 1] &] (* _G. C. Greubel_, Apr 23 2017 *)
%o (PARI) for(n=1,10^6, if(sigma(n)*omega(n)==sigma(n+1)*omega(n+1),print(n)))
%o (PARI) { n=0; s=1; for (m=1, 10^9, if(s!=(r=sigma(m)*omega(m)), s=r, write("b063071.txt", n++, " ", m - 1); if (n==100, break)) ) } \\ _Harry J. Smith_, Aug 16 2009
%Y Cf. A001221, A002961, A000203.
%K easy,nonn
%O 1,1
%A _Jason Earls_, Aug 04 2001