OFFSET
0,5
COMMENTS
A097801-base uses values 1, 2, 2*3, 2*3*5, 2*3*5*7, 2*3*5*7*9, 2*3*5*7*9*11, 2*3*5*7*9*11*13, 2*3*5*7*9*11*13*15, ..., for its digit-positions, instead of primorials (A002110), thus up to 1889 = 2*3*5*7*9 - 1 = 9*A002110(4) - 1 its representation is identical with the primorial base A049345. Therefore this sequence differs from A276153 for the first time at n=1890, where a(1890)=1, while A276153(1890)=9, as 1890 = 9*A002110(4).
Therefore this sequence might be produced as a rough approximation of A276153 by naive machine learning/mining algorithms. - Antti Karttunen, Mar 09 2021
LINKS
Antti Karttunen, Table of n, a(n) for n = 0..65537
EXAMPLE
In A097801-base, where the digit-positions are given by 1 and the terms of A097801 from its term a(1) onward: 2, 6, 30, 210, 1890, 20790, 270270, 4054050, ..., number 29 is expressed as "421" as 29 = 4*6 + 2*2 + 1*1, thus a(29) = 4. In the same base, number 30 is expressed as "1000" as 30 = 1*30, thus a(30) = 1.
Number 1890 = 2*3*5*7*9 is expressed as "100000", thus a(1890) = 1.
MATHEMATICA
Block[{nn = 105, b}, b = MixedRadix@ NestWhile[Prepend[#1, 2 #2 - 1] & @@ {#, Length[#] + 1} &, {2}, Times @@ # < nn &]; Array[First@ IntegerDigits[#, b] &, nn + 1, 0]] (* Michael De Vlieger, Feb 23 2021 *)
PROG
(PARI) A341356(n) = { my(m=2, k=3); while(n>=m, n \= m; m = k; k += 2); (n); }; \\ Antti Karttunen & Kevin Ryde, Feb 24 2021
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Antti Karttunen, Feb 23 2021
STATUS
approved