A064445 Numbers k such that sopf(k) - pi(k) = tau(k).

5, 39, 172, 305, 1182, 1194, 2947, 8936, 24363, 24399, 24417, 64730, 174977, 482028, 9559785, 9559905, 25876016, 25876976, 70113457, 189965322, 189967014, 189967122, 189967266, 189968202, 1394198020, 3779850963, 3779851593

Offset

1,1

Links

Table of n, a(n) for n=1..27.

Example

5 is in the sequence since sopf(5) - pi(5) = 5 - 3 = 2 = tau(5).

Prog

(PARI) sopf(n, fac) = fac=factor(n); sum(i=1, matsize(fac)[1], fac[i, 1]); pi(x, c) = forprime(p=2, x, c++); c for(n=1, 10^6, if(sopf(n)-pi(n)==numdiv(n), print(n)))

Crossrefs

Cf. A000005 (tau), A000720 (pi), A008472 (sopf).

Sequence in context: A153267 A183477 A219086 * A123614 A218918 A075135

Adjacent sequences: A064442 A064443 A064444 * A064446 A064447 A064448

Keyword

nonn

Author

Jason Earls, Oct 02 2001

Extensions

More terms from Klaus Brockhaus, Oct 05 2001. No further term < 800000.

Corrected offset and a(15)-a(27) from Donovan Johnson, Mar 10 2010

Status

approved