A063071 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).

14, 206, 1334, 1634, 2685, 14841, 18873, 19358, 26872, 33998, 36566, 42818, 56564, 84134, 116937, 122073, 161001, 162602, 166934, 174717, 190773, 193893, 239499, 245768, 260096, 289454, 326884, 383594, 409695, 422073, 430137, 438993, 440013

Offset

1,1

Links

Giovanni Resta, Table of n, a(n) for n = 1..1000 (first 100 terms from Harry J. Smith)

Mathematica

Select[Range[5000], PrimeNu[#]*DivisorSigma[1, #] == PrimeNu[# + 1]*DivisorSigma[1, # + 1] &] (* G. C. Greubel, Apr 23 2017 *)

Prog

(PARI) for(n=1, 10^6, if(sigma(n)*omega(n)==sigma(n+1)*omega(n+1), print(n)))
(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

Crossrefs

Cf. A001221, A002961, A000203.

Sequence in context: A349283 A333949 A002961 * A251963 A192007 A160682

Adjacent sequences: A063068 A063069 A063070 * A063072 A063073 A063074

Keyword

easy,nonn

Author

Jason Earls, Aug 04 2001

Status

approved