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A287059 Least numbers k > 1 such that k'' = n*k', where k' and k'' are the first and the second arithmetic derivatives of k. 0
2, 4, 12, 160, 1255, 256, 12279, 3072, 1113823, 119120, 2191040, 4640768, 1835008, 12805120, 134217728 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
LINKS
EXAMPLE
a(3) = 160 because 160'' / 160' = 1296 / 432 = 3 and this is the least number to have this property.
MAPLE
with(numtheory): P:=proc(q) local a, b, k, n, p; for n from 0 to q do
for k from 2 to q do a:=k*add(op(2, p)/op(1, p), p=ifactors(k)[2]); b:=a*add(op(2, p)/op(1, p), p=ifactors(a)[2]); if b=n*a then print(k); break;
fi; od; od; end: P(10^9);
CROSSREFS
Sequence in context: A053040 A154734 A291827 * A059085 A030064 A224886
KEYWORD
nonn,more
AUTHOR
Paolo P. Lava, May 19 2017
STATUS
approved

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Last modified June 13 17:32 EDT 2024. Contains 373391 sequences. (Running on oeis4.)