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%I #15 Oct 20 2021 08:02:55
%S 10,17,556,1771,4695,38537,56969,345797,141419115,1788191728
%N Numbers k such that 4^k starts with k.
%e 4^10 = 1048576 starts with 10, so 10 is in the sequence.
%p filter:= proc(n) local t, b;
%p t:= 4^n;
%p b:= ilog10(t) - ilog10(n);
%p floor(t/10^b) = n
%p end proc:
%p select(filter, [$1..10^5]);
%o (Python)
%o def afind(limit, startk=1):
%o k, pow4 = startk, 4**startk
%o for k in range(startk, limit+1):
%o if str(pow4).startswith(str(k)):
%o print(k, end=", ")
%o pow4 *= 4
%o afind(10**4) # _Michael S. Branicky_, Oct 17 2021
%Y Cf. A000302, A100129, A288845.
%K nonn,base,more
%O 1,1
%A _Robert Israel_, Oct 24 2018
%E a(8)-a(10) from _Giovanni Resta_, Oct 25 2018
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