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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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified January 26 22:05 EST 2022. Contains 350601 sequences. (Running on oeis4.)