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A102125 Iccanobirt numbers (15 of 15): a(n) = R(R(a(n-1)) + R(a(n-2)) + R(a(n-3))), where R is the digit reversal function A004086.

%I A102125 #15 Jul 22 2025 19:31:17
%S A102125 0,0,1,1,2,4,7,31,42,44,18,941,472,405,729,5071,6313,8675,90601,31591,
%T A102125 9853,11733,31865,31149,736481,365533,313416,3154311,9834802,5123383,
%U A102125 7112507,12796921,35055832,19867834,56610708,906334841,561210372
%N A102125 Iccanobirt numbers (15 of 15): a(n) = R(R(a(n-1)) + R(a(n-2)) + R(a(n-3))), where R is the digit reversal function A004086.
%C A102125 Digit reversal variation of tribonacci numbers A000073.
%C A102125 Inspired by Iccanobif numbers: A001129, A014258-A014260.
%H A102125 Alois P. Heinz, <a href="/A102125/b102125.txt">Table of n, a(n) for n = 0..1000</a>
%F A102125 a(n) = A004086(A102117(n)).
%p A102125 R:= n-> (s-> parse(cat(s[-i]$i=1..length(s))))(""||n):
%p A102125 a:= proc(n) option remember; `if`(n<3, binomial(n,2),
%p A102125       R(R(a(n-1)) + R(a(n-2)) + R(a(n-3))))
%p A102125     end:
%p A102125 seq(a(n), n=0..50);  # _Alois P. Heinz_, Jun 18 2014
%t A102125 R[n_]:=FromDigits[Reverse[IntegerDigits[n]]];Clear[a];a[0]=0;a[1]=0;a[2]=1;a [n_]:=a[n]=R[R[a[n-1]]+R[a[n-2]]+R[a[n-3]]];Table[a[n], {n, 0, 40}]
%t A102125 rev[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; nxt[{a_, b_, c_}] := {b, c, rev[rev[a] + rev[b] + rev[c]]}; Transpose[NestList[nxt,{0,0,1},40]][[1]] (* _Harvey P. Dale_, Mar 20 2015 *)
%t A102125 nxt[{a_,b_,c_}]:=With[{ir=IntegerReverse},{b,c,ir[ir[a]+ir[b]+ir[c]]}]; NestList[nxt,{0,0,1},40][[;;,1]] (* _Harvey P. Dale_, Jul 22 2025 *)
%Y A102125 Cf. A102111-A102124.
%K A102125 nonn,base,easy
%O A102125 0,5
%A A102125 _Jonathan Vos Post_ and _Ray Chandler_, Dec 30 2004