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A226779
Numbers n such that n'=(n+1)', where n' is the arithmetic derivative of n.
4
2, 777, 98433, 214388517, 152739317354
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OFFSET
1,1
COMMENTS
a(6) > 10^13. -
Giovanni Resta
, Mar 13 2014
a(6) > 5*10^13. -
Hiroaki Yamanouchi
, Aug 27 2015
LINKS
Table of n, a(n) for n=1..5.
EXAMPLE
2' = 3' = 1
777' = 778' = 391
98433' = 98434' = 65631
214388517' = 214388518' = 107194261
MAPLE
with(numtheory); ListA226779:=proc(q) local a, b, n, p; a:=0;
for n from 2 to q do b:=n*add(op(2, p)/op(1, p), p=ifactors(n)[2]);
if a=b then print(n-1); fi; a:=b; od; end: ListA226779(10^12);
CROSSREFS
Cf.
A003415
Sequence in context:
A167448
A320481
A078169
*
A243409
A281195
A109555
Adjacent sequences:
A226776
A226777
A226778
*
A226780
A226781
A226782
KEYWORD
nonn
,
more
AUTHOR
Paolo P. Lava
, Jun 18 2013
EXTENSIONS
a(5) from
Giovanni Resta
, Jun 18 2013
STATUS
approved
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Last modified August 14 11:25 EDT 2024. Contains 375159 sequences. (Running on oeis4.)