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A119238
Numbers k such that the decimal representation of k is contained as substring in that of the k-th triangular number.
2
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)
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
KEYWORD
base,nonn
AUTHOR
Giovanni Resta, May 10 2006
STATUS
approved