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

0, 1, 1, 2, 3, 5, 8, 13, 39, 124, 514, 836, 1053, 4139, 12815, 61135, 104937, 792517, 1454698, 9679838, 17354310, 9735140, 1760750, 986050, 621360, 113815, 581437, 1252496, 7676706, 13019288, 94367798, 178067380, 173537220, 106496242, 265429972, 522619163

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• base
• easy
• nice

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..1000 (terms 0..300 from T. D. Noe)

Crossrefs

Cf. A001129, A014258, A014259, A014260.

Programs

Haskell

a001129 n = a001129_list !! n
a001129_list = 0 : 1 : zipWith (+) iccanobifs (tail iccanobifs) where iccanobifs = map a004086 a001129_list
-- Reinhard Zumkeller, Jan 01 2012

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

Maple

R:= n-> (s-> parse(cat(s[-i]$i=1..length(s))))(""||n):
a:= proc(n) option remember; `if`(n<2, n,
       R(a(n-1)) +R(a(n-2)))
    end:
seq(a(n), n=0..50);  # Alois P. Heinz, Jun 18 2014

Mathematica

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 ]
nxt[{a_,b_}]:={b,Total[FromDigits/@Reverse/@IntegerDigits[ {a,b}]]}; Transpose[NestList[nxt,{0,1},40]][[1]] (* Harvey P. Dale, Jun 22 2011 *)
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 *)

PARI

A001129(n,a=0,b=1)={ n || return; while( n-->0, b=A004086(a)+A004086(a=b)); b }

Python

A001129_list, r1, r2 = [0,1], 1, 0
for _ in range(10**2):
    l, r2 = r1+r2, r1
    r1 = int(str(l)[::-1])
    A001129_list.append(l) # Chai Wah Wu, Jan 03 2015