Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #13 Jan 03 2020 04:36:17
%S 1,4,61,442,8671,48643,275491,4691011,44046781,421781671,4866217861,
%T 44417846491,469583176771,4807072338781,42155398282291,
%U 461921395126861,4447050855867481,42996432430288771,480551127927589171,4866530171154022291,46198061648602166491
%N Numbers multiplied by 4 and written backwards.
%H Alois P. Heinz, <a href="/A132064/b132064.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = reverse(4*a(n-1)) where a(1) = 1
%F Conjecture: a(n)^(1/n) tends to 10. - _Vaclav Kotesovec_, Jan 03 2020
%e a(4) = reverse(4*a(3)) = reverse(4*reverse(4*a(2))) = reverse(4*reverse(4*reverse(4*a(1)))) = reverse(4*reverse(4*4)) = reverse(4*61) = reverse(244) = 442
%p a:= proc(n) option remember; `if`(n=1, 1,
%p (s-> parse(cat(s[-i]$i=1..length(s))))(""||(4*a(n-1))))
%p end:
%p seq(a(n), n=1..30); # _Alois P. Heinz_, Apr 09 2015
%t NestList[IntegerReverse[4#]&,1,20] (* Requires Mathematica version 11 or later *) (* _Harvey P. Dale_, Dec 09 2017 *)
%Y Cf. A036447 (*2), A163632 (*3), A045539 (*5), A132078 (*6), A132114 (*7), A132113 (*8), A133361 (*9).
%K base,nonn
%O 1,2
%A Rachit Agrawal (rachit_agrawal(AT)daiict.ac.in), Oct 30 2007
%E More terms from _Alois P. Heinz_, Apr 09 2015