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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.
7
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
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
KEYWORD
nonn,base,easy
AUTHOR
STATUS
approved