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A001129 Iccanobif numbers: reverse digits of two previous terms and add.

%I A001129 #59 Jul 05 2025 05:22:31
%S A001129 0,1,1,2,3,5,8,13,39,124,514,836,1053,4139,12815,61135,104937,792517,
%T A001129 1454698,9679838,17354310,9735140,1760750,986050,621360,113815,581437,
%U A001129 1252496,7676706,13019288,94367798,178067380,173537220,106496242,265429972,522619163
%N A001129 Iccanobif numbers: reverse digits of two previous terms and add.
%H A001129 Alois P. Heinz, <a href="/A001129/b001129.txt">Table of n, a(n) for n = 0..1000</a> (terms 0..300 from T. D. Noe)
%p A001129 R:= n-> (s-> parse(cat(s[-i]$i=1..length(s))))(""||n):
%p A001129 a:= proc(n) option remember; `if`(n<2, n,
%p A001129        R(a(n-1)) +R(a(n-2)))
%p A001129     end:
%p A001129 seq(a(n), n=0..50);  # _Alois P. Heinz_, Jun 18 2014
%t A001129 Clear[ BIF ]; BIF[ 0 ]=0; BIF[ 1 ]=1; BIF[ n_Integer ] := BIF[ n ]=Plus@@Map[ Plus@@(#*Array[ 10^#&, Length[ # ], 0 ])&, Map[ IntegerDigits, {BIF[ n-1 ], BIF[ n-2 ]} ] ]; Array[ BIF, 40, 0 ]
%t A001129 nxt[{a_,b_}]:={b,Total[FromDigits/@Reverse/@IntegerDigits[ {a,b}]]}; Transpose[NestList[nxt,{0,1},40]][[1]] (* _Harvey P. Dale_, Jun 22 2011 *)
%t A001129 nxt[{a_,b_}]:={b,Total[IntegerReverse[{a,b}]]}; NestList[nxt,{0,1},40][[All,1]] (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Aug 07 2019 *)
%o A001129 (PARI) A001129(n,a=0,b=1)={ n || return; while( n-->0, b=A004086(a)+A004086(a=b)); b }
%o A001129 (Haskell)
%o A001129 a001129 n = a001129_list !! n
%o A001129 a001129_list = 0 : 1 : zipWith (+) iccanobifs (tail iccanobifs) where iccanobifs = map a004086 a001129_list
%o A001129 -- _Reinhard Zumkeller_, Jan 01 2012
%o A001129 (Python)
%o A001129 A001129_list, r1, r2 = [0,1], 1, 0
%o A001129 for _ in range(10**2):
%o A001129     l, r2 = r1+r2, r1
%o A001129     r1 = int(str(l)[::-1])
%o A001129     A001129_list.append(l) # _Chai Wah Wu_, Jan 03 2015
%o A001129 (Magma) a:=[0,1];[n le 2 select a[n] else Seqint(Reverse(Intseq(Self(n-1)))) + Seqint(Reverse(Intseq(Self(n-2)))):n in [1..35]]; // _Marius A. Burtea_, Oct 23 2019
%Y A001129 Cf. A001129, A014258, A014259, A014260.
%K A001129 nonn,base,easy,nice
%O A001129 0,4
%A A001129 _N. J. A. Sloane_