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a(n) = n_n, where "N_b" denotes "N read in base b": if N = Sum c_i 10^i then N_b = Sum c_i b^i.
33

%I #23 Jul 04 2022 07:59:57

%S 1,2,3,4,5,6,7,8,9,10,12,14,16,18,20,22,24,26,28,40,43,46,49,52,55,58,

%T 61,64,67,90,94,98,102,106,110,114,118,122,126,160,165,170,175,180,

%U 185,190,195,200,205,250,256,262,268,274,280,286,292,298,304,360,367,374,381,388

%N a(n) = n_n, where "N_b" denotes "N read in base b": if N = Sum c_i 10^i then N_b = Sum c_i b^i.

%C The definition applies even if b < 10. Examples: 23_45 = 2*45 + 3 = 93, 23_2 = 2*2 + 3 = 7.

%D David Applegate, Marc LeBrun and N. J. A. Sloane, Descending Dungeons and Iterated Base-Changing, in "The Mathematics of Preference, Choice and Order: Essays in Honor of Peter Fishburn", edited by Steven Brams, William V. Gehrlein and Fred S. Roberts, Springer, 2009, pp. 393-402.

%H N. J. A. Sloane, <a href="/A122618/b122618.txt">Table of n, a(n) for n = 1..10000</a>

%H David Applegate, Marc LeBrun and N. J. A. Sloane, <a href="https://arxiv.org/abs/math/0611293">Descending Dungeons and Iterated Base-Changing</a>, arXiv:math/0611293 [math.NT], 2006-2007.

%H David Applegate, Marc LeBrun, N. J. A. Sloane, <a href="https://www.jstor.org/stable/40391135">Descending Dungeons, Problem 11286</a>, Amer. Math. Monthly, 116 (2009) 466-467.

%p A122618 := proc(n)

%p local dgs;

%p dgs := convert(n,base,10) ;

%p add(op(i,dgs)*n^(i-1),i=1..nops(dgs)) ;

%p end proc: # _R. J. Mathar_, May 06 2019

%t f[n_] := FromDigits[ IntegerDigits@n, n]; Array[f, 64] (* _Robert G. Wilson v_, Sep 27 2006 *)

%o (PARI) A122618(n,d=digits(n))=d*vectorv(#d,i,n^(#d-i)) \\ _M. F. Hasler_, Apr 22 2015

%Y Differs from A083292 starting at n=100.

%Y Cf. A028897 (n_2), A122640 (2n_2).

%K nonn,base,easy

%O 1,2

%A _N. J. A. Sloane_, Sep 21 2006