A119398 Odd numbers taking exactly 21 steps to reach 15 in A086793.

628425, 824175, 1340325, 1422135, 1495725, 1729665, 1845585, 1853775, 1916145, 2001825, 2015685, 2040675, 2045505, 2091375, 2165625, 2220435, 2226609, 2264535, 2333925, 2360085, 2365965, 2379465, 2465925, 2474955, 2499255, 2511495

Offset: 1

Author

Zak Seidov, May 18 2006

Keywords

• base
• nonn

Comments

Most terms are multiples of 5. In the first 130 terms, there only 19 non-multiples of 5: 2226609, 2556477, 3252249, 3496779, 3638439, 4060287, 4779621, 4821453, 5146713, 5313231, 5365899, 5504499, 5578419, 5738733, 5785857, 5845749, 6189183, 6222447, 6236769.

Links

• Robert Israel, Table of n, a(n) for n = 1..500

Crossrefs

Cf. A086793, A119396-A119415.

Programs

Maple

f:= proc(n) option remember; local t;
  if kernelopts(level) > 460 then return FAIL fi;
  t:= add(convert(convert(d,base,10),`+`),d=numtheory:-divisors(n));
  1+procname(t)
end proc:
f(15):= 0:
f(1):= FAIL:
Res:= NULL: count:= 0:
for n from 1 by 2 while count < 100 do
  if f(n) = 21 then Res:= Res, n; count:= count+1 fi;
od:
Res; # Robert Israel, Apr 03 2018

Extensions

a(1)=628425 inserted by Robert Israel, Apr 03 2018