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A119398
Odd numbers taking exactly 21 steps to reach 15 in A086793.
3
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
1,1
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
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
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Zak Seidov, May 18 2006
EXTENSIONS
a(1)=628425 inserted by Robert Israel, Apr 03 2018
STATUS
approved