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A284813
Numbers n such that n' = d_1^k + d_2^(k-2) + ... + d_k^1 where d_1, d_2, ..., d_k are the digits of n, with MSD(n) = d_1 and LSD(n) = d_k, and n' is the arithmetic derivative of n.
0
4, 766, 2587, 12629, 104977, 1068623, 1844423, 2056849, 2089207, 3126943, 3216923, 3410107, 11894353, 14467237, 20409227, 20544577, 23417957, 53531447, 57145091
OFFSET
1,1
EXAMPLE
766' = 385 = 7^3 + 6^2 + 6^1.
MAPLE
with(numtheory): P:=proc(q) local a, k, n, p; for n from 1 to q do a:=convert(n, base, 10);
if add(a[k]^k, k=1..nops(a))=n*add(op(2, p)/op(1, p), p=ifactors(n)[2])
then print(n); fi; od; end: P(10^9);
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Paolo P. Lava, Apr 07 2017
STATUS
approved