A119042 - OEIS

%I #13 Sep 08 2022 08:45:25

%S 1,3,4,11,36,141,179,363,1095,3633,4473,4704,36333,44758,46079,46904,

%T 57620,1414920,1460141,4474371,14560288,348310541,1822424761720,

%U 34670191840011,471172177895936,4472359691719799

%N Numbers k such that the k-th triangular number contains only digits {0,1,6}.

%C Next term exceeds 1.4*10^16.

%H G. Resta, <a href="http://www.numbersaplenty.com/tr/tr016.html">Tridigital Triangular Numbers</a>

%t Select[Range[2 10^7], Complement[IntegerDigits[Binomial[# + 1, 2]], {0, 1, 6}] == {} &] (* _Vincenzo Librandi_, Dec 25 2015 *)

%o (Magma) [n: n in [1..2*10^7] | Set(Intseq(Binomial(n+1, 2))) subset [0, 1, 6]]; // _Vincenzo Librandi_, Dec 25 2015

%Y Cf. A000217, A119041. See A119034 for a table of cross-references.

%K nonn,base,more

%O 1,2

%A _Giovanni Resta_, May 10 2006