A336768 - OEIS

%I #25 Aug 06 2020 04:09:24

%S 1,1,2,22,1,2,3,7,22,1,2,3,4,7,22,87,9831,1,2,3,4,5,7,9,17,22,51,87,

%T 102,2601,9831,314767045,1,2,3,4,5,6,7,9,17,22,51,87,91,102,220,2601,

%U 5258,7491,8283,9831,10516,13541,15774,16566,71500,644765,3552340,314767045,1427310725,1848187230,1916060910

%N Irregular triangle where the n-th row list the positive integers which can be written in two bases smaller than n as mutually-reversed strings of digit(s), for n>=4.

%C Note that the last row with index 9 may still be incomplete.

%C If k is in row n then k is in row n+1. - _David A. Corneth_, Aug 04 2020

%e Triangle begins:

%e 4| 1;

%e 5| 1, 2, 22;

%e 6| 1, 2, 3, 7, 22;

%e 7| 1, 2, 3, 4, 7, 22, 87, 9831;

%e 8| 1, 2, 3, 4, 5, 7, 9, 17, 22, 51, 87, 102, 2601, 9831, 314767045;

%e 9| 1, 2, 3, 4, 5, 6, 7, 9, 17, 22, 51, 87, 91, 102, 220, 2601, 5258, 7491, ...

%e ...

%e For n=4, there is a single integer whose base 2 and base 3 representations are each other reverse: it is 1 which is its own reverse.

%Y Cf. A336733 (row index 10), A336827 (right diagonal).

%K nonn,base,tabf

%O 4,3

%A _Michel Marcus_, Aug 04 2020

%E a(32) from _Graham Holmes_, Aug 04 2020

%E More terms from _Jinyuan Wang_, Aug 04 2020