S000358


Palindromic triangular numbers in base 8.

1, 3, 6, 44, 55, 151, 424, 454, 505, 626, 4774, 7777, 13731, 21112, 27472, 37073, 40704, 62426, 167761, 516615, 725527, 2773772, 3535353, 4053504, 4733374, 6063606, 6244426, 6427246, 24355342, 42322324, 51355315, 70000007, 102121201, 120414021, 137000731

1

S000358

See S000350 for the n that produce these triangular numbers.

T. D. Noe, Plot of 176 terms

T. D. Noe, Table of 176 terms

Eric W. Weisstein, MathWorld: Triangular Number

(Mma) ff[base_, len_] := Module[{n = 0, t = {}, tri, d}, While[Length[t] < len, n++; tri = n*(n + 1)/2; d = IntegerDigits[tri, base]; If[d == Reverse[d], AppendTo[t, n]]]; t]; t8 = ff[8, 40]; Table[FromDigits[IntegerDigits[n*(n + 1)/2, 8]], {n, t8}]

Cf. S000350.

nonn,base,hard

T. D. Noe, Nov 19 2014

© Tony D Noe 2014-2015