A336733 -id:A336733 - cp's OEIS frontend

A336768 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.

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, 102, 2601, 9831, 314767045, 1, 2, 3, 4, 5, 6, 7, 9, 17, 22, 51, 87, 91, 102, 220, 2601, 5258, 7491, 8283, 9831, 10516, 13541, 15774, 16566, 71500, 644765, 3552340, 314767045, 1427310725, 1848187230, 1916060910

Offset: 4

Michel Marcus, Aug 04 2020

If k is in row n then k is in row n+1. - David A. Corneth, Aug 04 2020

			Triangle begins:
  4| 1;
  5| 1, 2, 22;
  6| 1, 2, 3, 7, 22;
  7| 1, 2, 3, 4, 7, 22, 87, 9831;
  8| 1, 2, 3, 4, 5, 7, 9, 17, 22, 51, 87, 102, 2601, 9831, 314767045;
  9| 1, 2, 3, 4, 5, 6, 7, 9, 17, 22, 51, 87, 91, 102, 220, 2601, 5258, 7491, ...
  ...
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.

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

a(32) from Graham Holmes, Aug 04 2020

More terms from Jinyuan Wang, Aug 04 2020

A336827 a(n) is the largest integer that can be written in two bases smaller than n as mutually-reversed strings of digit(s), for n>=4.

Original entry on oeis.org

1, 22, 22, 9831, 314767045, 1916060910, 455075911977

Offset: 4

Michel Marcus, Aug 05 2020

			a(5) is 22 because 22 = 211 (base 3) = 112 (base 4) is the largest such integer with both bases < 5 (here 3 and 4).
a(6) is also 22 because there are no larger such integers with both bases < 6.
a(7) is 9831 because 9831 = 303311 (base 5) and 113303 (base 6) is the largest such integer with both bases < 7 (here 5 and 6).

Cf. A336733, A336768.

a(9)-a(10) from Bert Dobbelaere, Sep 20 2020

cp's OEIS Frontend

A336768 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.

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