A119396 -id:A119396 - cp's OEIS frontend

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

Zak Seidov, May 18 2006

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.

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

Cf. A086793, A119396-A119415.

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

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

A119397 Numbers taking exactly 21 steps to reach 15 in A086793.

Original entry on oeis.org

71820, 103950, 127764, 135660, 141360, 161460, 173250, 183744, 193284, 203580, 206712, 209440, 214830, 217620, 221760, 223020, 223860, 234432, 243540, 244440, 246330, 247752, 256680, 263160, 264180, 265200, 280368, 281160, 286380, 287712

Offset: 1

Zak Seidov, May 18 2006

Some trajectories are: 71820,1104,168,102,36,46,18,30,27,22,9,13,5,6,12,19,11,3,4,7,8,15 103950,1134,168,... 127764,924,168,... 135660,1134,168,... 221760,1908,162,66,36,... 343728,1650,162,... 376992,2016,297,66,36,... All trajectories eventually join one of previous trajectories. In the first 136 terms <800000 there is only one odd number, 628425. Next odd terms are: 824175, 1340325, 1422135, 1495725 (see A119398).

Cf. A086793, A119396-A119415.

cp's OEIS Frontend

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

Views

Author

Keywords

Comments

Links

Crossrefs

Programs

Maple