A102113 Iccanobirt numbers (3 of 15): a(n) = a(n-1) + R(a(n-2)) + R(a(n-3)), where R is the digit reversal function A004086.

0, 0, 1, 1, 2, 4, 7, 13, 24, 62, 135, 203, 760, 1593, 1962, 5980, 12622, 16208, 39724, 142606, 265660, 914694, 1587497, 2150478, 10594748, 27283111, 120773124, 216660897, 649176190, 1868619823, 2758358381, 6139199008, 11266906261

Offset

0,5

Comments

Digit reversal variation of tribonacci numbers A000073.

Inspired by Iccanobif numbers: A001129, A014258-A014260.

Links

Alois P. Heinz, Table of n, a(n) for n = 0..1000

Formula

A004086(a(n)) = A102121(n).

Maple

R:= n-> (s-> parse(cat(s[-i]$i=1..length(s))))(""||n):
a:= proc(n) option remember; `if`(n<3, binomial(n, 2),
       a(n-1) + R(a(n-2)) + R(a(n-3)) )
    end:
seq(a(n), n=0..50);  # Alois P. Heinz, Jun 18 2014

Mathematica

R[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; Clear[a]; a[0]=0; a[1]=0; a[2]=1; a [n_]:=a[n]=a[n-1]+R[a[n-2]]+R[a[n-3]]; Table[a[n], {n, 0, 40}]
nxt[{a1_, a2_, a3_}]:={a2, a3, a3+FromDigits[Reverse[IntegerDigits[ a1]]]+ FromDigits[ Reverse[ IntegerDigits[a2]]]}; Transpose[NestList[nxt, {0, 0, 1}, 40]][[1]] (* Harvey P. Dale, Oct 17 2012 *)
nxt[{a_, b_, c_}]:={b, c, c+IntegerReverse[b]+IntegerReverse[a]}; NestList[ nxt, {0, 0, 1}, 40][[All, 1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 10 2016 *)

Crossrefs

Cf. A102111-A102125.

Sequence in context: A127602 A113291 A102112 * A034440 A358334 A000074

Adjacent sequences: A102110 A102111 A102112 * A102114 A102115 A102116

Keyword

nonn,base,easy

Author

Jonathan Vos Post and Ray Chandler, Dec 30 2004

Status

approved