A119238 Numbers k such that the decimal representation of k is contained as substring in that of the k-th triangular number.

1, 5, 19, 25, 199, 625, 1999, 2102, 5582, 9376, 9909, 10100, 16833, 19999, 41012, 55741, 74491, 83885, 88102, 90625, 151774, 199999, 201002, 558257, 626522, 740312, 798097, 810062, 890625, 1001000, 1030563, 1668333, 1999999, 2646751

Offset

1,2

Links

Giovanni Resta, Table of n, a(n) for n = 1..101 (terms < 10^12)

Maple

select(n->searchtext(convert(n, string), convert(n*(n+1)/2, string))>0, [$0..10^5]); # Paolo P. Lava, Jun 27 2018

Mathematica

Select[Range@100000, ({}!=StringPosition[ToString[ #(#+1)/2], ToString@# ]) &]
Select[Range[3*10^6], SequenceCount[IntegerDigits[(#(#+1))/2], IntegerDigits[ #]]>0&] (* The program uses the SequenceCount function from Mathematica version 10 *) (* Harvey P. Dale, Dec 26 2015 *)

Crossrefs

Cf. A046831.

Sequence in context: A022143 A004623 A018475 * A218885 A198791 A332155

Adjacent sequences: A119235 A119236 A119237 * A119239 A119240 A119241

Keyword

base,nonn

Author

Giovanni Resta, May 10 2006

Status

approved