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%I #59 Jun 09 2021 02:42:29
%S 1,428,573,725,727,738,846,7810,8093,28023,36354,36365,36464,63636,
%T 254544,277851,297422,326734,673267,673368,2889810,4545454,4545465,
%U 5454547,5454646,24275425,29411775,47058823,52941178,94117748,146407310,263157795,267735365,285714186
%N Positive numbers k such that the decimal expansion of k^2 appears in the concatenation of the first k positive integers.
%C A030467 is a subsequence. - _Chai Wah Wu_, Jun 07 2021
%H Chai Wah Wu, <a href="/A343536/b343536.txt">Table of n, a(n) for n = 1..116</a>
%e 428^2 = 183184, which appears in the concatenation of the first 428 positive integers at 183,184, i.e., (183184), so 428 is a term.
%e 725^2 = 525625, which appears in the concatenation of the first 725 positive integers at 255,256,257, i.e., 25(525625)7, so 725 is a term.
%t Select[Range@1000,StringContainsQ[""<>ToString/@Range@#,ToString[#^2]]&] (* _Giorgos Kalogeropoulos_, Apr 24 2021 *)
%o (Java)
%o public class Oeis2 {
%o public static void main(String[] args) {
%o StringBuilder str = new StringBuilder();
%o long n = 1;
%o while (true) {
%o str.append(n);
%o if (str.indexOf(String.valueOf(n * n)) >= 0) {
%o System.out.print(n + ", ");
%o }
%o n++;
%o }
%o }
%o }
%o (PARI) f(n) = my(s=""); for(k=1, n, s=Str(s, k)); s; \\ from A007908
%o isok(k) = #strsplit(f(k), Str(k^2)) > 1; \\ _Michel Marcus_, May 02 2021
%o (Python)
%o A343536_list, k, s = [], 1, '1'
%o while k < 10**6:
%o if str(k**2) in s:
%o A343536_list.append(k)
%o k += 1
%o s += str(k) # _Chai Wah Wu_, Jun 06 2021
%Y Cf. A007908, A030467, A259379.
%K nonn,base
%O 1,2
%A _John R Phelan_, Apr 18 2021
%E More terms from _Jinyuan Wang_, Apr 30 2021